Identifier
-
Mp00014:
Binary trees
—to 132-avoiding permutation⟶
Permutations
Mp00248: Permutations —DEX composition⟶ Integer compositions
Mp00184: Integer compositions —to threshold graph⟶ Graphs
St000455: Graphs ⟶ ℤ
Values
[.,[.,[.,.]]] => [3,2,1] => [2,1] => ([(0,2),(1,2)],3) => 0
[.,[.,[[.,.],.]]] => [3,4,2,1] => [3,1] => ([(0,3),(1,3),(2,3)],4) => 0
[.,[[.,.],[.,.]]] => [4,2,3,1] => [3,1] => ([(0,3),(1,3),(2,3)],4) => 0
[.,[[.,[.,.]],.]] => [3,2,4,1] => [2,2] => ([(1,3),(2,3)],4) => 0
[[.,.],[.,[.,.]]] => [4,3,1,2] => [1,3] => ([(2,3)],4) => 0
[[.,[.,.]],[.,.]] => [4,2,1,3] => [2,2] => ([(1,3),(2,3)],4) => 0
[[.,[.,[.,.]]],.] => [3,2,1,4] => [2,2] => ([(1,3),(2,3)],4) => 0
[.,[.,[.,[[.,.],.]]]] => [4,5,3,2,1] => [3,1,1] => ([(0,3),(0,4),(1,3),(1,4),(2,3),(2,4),(3,4)],5) => 0
[.,[.,[[[.,.],.],.]]] => [3,4,5,2,1] => [4,1] => ([(0,4),(1,4),(2,4),(3,4)],5) => 0
[.,[[.,.],[[.,.],.]]] => [4,5,2,3,1] => [4,1] => ([(0,4),(1,4),(2,4),(3,4)],5) => 0
[.,[[[.,.],.],[.,.]]] => [5,2,3,4,1] => [4,1] => ([(0,4),(1,4),(2,4),(3,4)],5) => 0
[.,[[.,[[.,.],.]],.]] => [3,4,2,5,1] => [3,2] => ([(1,4),(2,4),(3,4)],5) => 0
[.,[[[.,.],[.,.]],.]] => [4,2,3,5,1] => [3,2] => ([(1,4),(2,4),(3,4)],5) => 0
[.,[[[.,[.,.]],.],.]] => [3,2,4,5,1] => [2,3] => ([(2,4),(3,4)],5) => 0
[[.,.],[.,[[.,.],.]]] => [4,5,3,1,2] => [3,2] => ([(1,4),(2,4),(3,4)],5) => 0
[[.,.],[[.,.],[.,.]]] => [5,3,4,1,2] => [1,4] => ([(3,4)],5) => 0
[[.,.],[[.,[.,.]],.]] => [4,3,5,1,2] => [1,4] => ([(3,4)],5) => 0
[[.,[.,.]],[[.,.],.]] => [4,5,2,1,3] => [3,2] => ([(1,4),(2,4),(3,4)],5) => 0
[[[.,.],.],[.,[.,.]]] => [5,4,1,2,3] => [1,4] => ([(3,4)],5) => 0
[[.,[[.,.],.]],[.,.]] => [5,2,3,1,4] => [3,2] => ([(1,4),(2,4),(3,4)],5) => 0
[[[.,.],[.,.]],[.,.]] => [5,3,1,2,4] => [1,4] => ([(3,4)],5) => 0
[[[.,[.,.]],.],[.,.]] => [5,2,1,3,4] => [2,3] => ([(2,4),(3,4)],5) => 0
[[.,[.,[[.,.],.]]],.] => [3,4,2,1,5] => [3,2] => ([(1,4),(2,4),(3,4)],5) => 0
[[.,[[.,.],[.,.]]],.] => [4,2,3,1,5] => [3,2] => ([(1,4),(2,4),(3,4)],5) => 0
[[.,[[.,[.,.]],.]],.] => [3,2,4,1,5] => [2,3] => ([(2,4),(3,4)],5) => 0
[[[.,.],[.,[.,.]]],.] => [4,3,1,2,5] => [1,4] => ([(3,4)],5) => 0
[[[.,[.,.]],[.,.]],.] => [4,2,1,3,5] => [2,3] => ([(2,4),(3,4)],5) => 0
[[[.,[.,[.,.]]],.],.] => [3,2,1,4,5] => [2,3] => ([(2,4),(3,4)],5) => 0
[.,[.,[.,[[[.,.],.],.]]]] => [4,5,6,3,2,1] => [4,1,1] => ([(0,4),(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6) => 0
[.,[.,[[.,.],[[.,.],.]]]] => [5,6,3,4,2,1] => [4,1,1] => ([(0,4),(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6) => 0
[.,[.,[[[[.,.],.],.],.]]] => [3,4,5,6,2,1] => [5,1] => ([(0,5),(1,5),(2,5),(3,5),(4,5)],6) => 0
[.,[[.,.],[[[.,.],.],.]]] => [4,5,6,2,3,1] => [5,1] => ([(0,5),(1,5),(2,5),(3,5),(4,5)],6) => 0
[.,[[[.,.],.],[[.,.],.]]] => [5,6,2,3,4,1] => [5,1] => ([(0,5),(1,5),(2,5),(3,5),(4,5)],6) => 0
[.,[[[[.,.],.],.],[.,.]]] => [6,2,3,4,5,1] => [5,1] => ([(0,5),(1,5),(2,5),(3,5),(4,5)],6) => 0
[.,[[.,[.,[[.,.],.]]],.]] => [4,5,3,2,6,1] => [3,1,2] => ([(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6) => 0
[.,[[.,[[[.,.],.],.]],.]] => [3,4,5,2,6,1] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[.,[[[.,.],[[.,.],.]],.]] => [4,5,2,3,6,1] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[.,[[[[.,.],.],[.,.]],.]] => [5,2,3,4,6,1] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[.,[[[.,[[.,.],.]],.],.]] => [3,4,2,5,6,1] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[.,[[[[.,.],[.,.]],.],.]] => [4,2,3,5,6,1] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[.,[[[[.,[.,.]],.],.],.]] => [3,2,4,5,6,1] => [2,4] => ([(3,5),(4,5)],6) => 0
[[.,.],[.,[[[.,.],.],.]]] => [4,5,6,3,1,2] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[[.,.],[[.,.],[[.,.],.]]] => [5,6,3,4,1,2] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[[.,.],[[[.,.],.],[.,.]]] => [6,3,4,5,1,2] => [1,5] => ([(4,5)],6) => 0
[[.,.],[[.,[[.,.],.]],.]] => [4,5,3,6,1,2] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[.,.],[[[.,.],[.,.]],.]] => [5,3,4,6,1,2] => [1,5] => ([(4,5)],6) => 0
[[.,.],[[[.,[.,.]],.],.]] => [4,3,5,6,1,2] => [1,5] => ([(4,5)],6) => 0
[[.,[.,.]],[[[.,.],.],.]] => [4,5,6,2,1,3] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[[[.,.],.],[.,[.,[.,.]]]] => [6,5,4,1,2,3] => [1,1,4] => ([(3,4),(3,5),(4,5)],6) => 0
[[[.,.],.],[.,[[.,.],.]]] => [5,6,4,1,2,3] => [2,4] => ([(3,5),(4,5)],6) => 0
[[[.,.],.],[[.,.],[.,.]]] => [6,4,5,1,2,3] => [1,5] => ([(4,5)],6) => 0
[[[.,.],.],[[.,[.,.]],.]] => [5,4,6,1,2,3] => [1,5] => ([(4,5)],6) => 0
[[.,[.,[.,.]]],[[.,.],.]] => [5,6,3,2,1,4] => [3,1,2] => ([(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6) => 0
[[.,[[.,.],.]],[[.,.],.]] => [5,6,2,3,1,4] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[[[.,.],[.,.]],[[.,.],.]] => [5,6,3,1,2,4] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[[.,[.,.]],.],[[.,.],.]] => [5,6,2,1,3,4] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[[[.,.],.],.],[.,[.,.]]] => [6,5,1,2,3,4] => [1,5] => ([(4,5)],6) => 0
[[.,[[[.,.],.],.]],[.,.]] => [6,2,3,4,1,5] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[[[.,.],[[.,.],.]],[.,.]] => [6,3,4,1,2,5] => [1,5] => ([(4,5)],6) => 0
[[[[.,.],.],[.,.]],[.,.]] => [6,4,1,2,3,5] => [1,5] => ([(4,5)],6) => 0
[[[.,[[.,.],.]],.],[.,.]] => [6,2,3,1,4,5] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[[[.,.],[.,.]],.],[.,.]] => [6,3,1,2,4,5] => [1,5] => ([(4,5)],6) => 0
[[[[.,[.,.]],.],.],[.,.]] => [6,2,1,3,4,5] => [2,4] => ([(3,5),(4,5)],6) => 0
[[.,[.,[.,[[.,.],.]]]],.] => [4,5,3,2,1,6] => [3,1,2] => ([(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6) => 0
[[.,[.,[[[.,.],.],.]]],.] => [3,4,5,2,1,6] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[[.,[[.,.],[[.,.],.]]],.] => [4,5,2,3,1,6] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[[.,[[[.,.],.],[.,.]]],.] => [5,2,3,4,1,6] => [4,2] => ([(1,5),(2,5),(3,5),(4,5)],6) => 0
[[.,[[.,[[.,.],.]],.]],.] => [3,4,2,5,1,6] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[.,[[[.,.],[.,.]],.]],.] => [4,2,3,5,1,6] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[.,[[[.,[.,.]],.],.]],.] => [3,2,4,5,1,6] => [2,4] => ([(3,5),(4,5)],6) => 0
[[[.,.],[.,[[.,.],.]]],.] => [4,5,3,1,2,6] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[[.,.],[[.,.],[.,.]]],.] => [5,3,4,1,2,6] => [1,5] => ([(4,5)],6) => 0
[[[.,.],[[.,[.,.]],.]],.] => [4,3,5,1,2,6] => [1,5] => ([(4,5)],6) => 0
[[[.,[.,.]],[[.,.],.]],.] => [4,5,2,1,3,6] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[[[.,.],.],[.,[.,.]]],.] => [5,4,1,2,3,6] => [1,5] => ([(4,5)],6) => 0
[[[.,[[.,.],.]],[.,.]],.] => [5,2,3,1,4,6] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[[[.,.],[.,.]],[.,.]],.] => [5,3,1,2,4,6] => [1,5] => ([(4,5)],6) => 0
[[[[.,[.,.]],.],[.,.]],.] => [5,2,1,3,4,6] => [2,4] => ([(3,5),(4,5)],6) => 0
[[[.,[.,[[.,.],.]]],.],.] => [3,4,2,1,5,6] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[[.,[[.,.],[.,.]]],.],.] => [4,2,3,1,5,6] => [3,3] => ([(2,5),(3,5),(4,5)],6) => 0
[[[.,[[.,[.,.]],.]],.],.] => [3,2,4,1,5,6] => [2,4] => ([(3,5),(4,5)],6) => 0
[[[[.,.],[.,[.,.]]],.],.] => [4,3,1,2,5,6] => [1,5] => ([(4,5)],6) => 0
[[[[.,[.,.]],[.,.]],.],.] => [4,2,1,3,5,6] => [2,4] => ([(3,5),(4,5)],6) => 0
[[[[.,[.,[.,.]]],.],.],.] => [3,2,1,4,5,6] => [2,4] => ([(3,5),(4,5)],6) => 0
[.,[.,[.,[.,[[[.,.],.],.]]]]] => [5,6,7,4,3,2,1] => [4,1,1,1] => ([(0,4),(0,5),(0,6),(1,4),(1,5),(1,6),(2,4),(2,5),(2,6),(3,4),(3,5),(3,6),(4,5),(4,6),(5,6)],7) => 0
[.,[.,[.,[[[[.,.],.],.],.]]]] => [4,5,6,7,3,2,1] => [5,1,1] => ([(0,5),(0,6),(1,5),(1,6),(2,5),(2,6),(3,5),(3,6),(4,5),(4,6),(5,6)],7) => 0
[.,[.,[[.,.],[[[.,.],.],.]]]] => [5,6,7,3,4,2,1] => [5,1,1] => ([(0,5),(0,6),(1,5),(1,6),(2,5),(2,6),(3,5),(3,6),(4,5),(4,6),(5,6)],7) => 0
[.,[.,[[[.,.],.],[[.,.],.]]]] => [6,7,3,4,5,2,1] => [5,1,1] => ([(0,5),(0,6),(1,5),(1,6),(2,5),(2,6),(3,5),(3,6),(4,5),(4,6),(5,6)],7) => 0
[.,[.,[[[[[.,.],.],.],.],.]]] => [3,4,5,6,7,2,1] => [6,1] => ([(0,6),(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[.,.],[[[[.,.],.],.],.]]] => [4,5,6,7,2,3,1] => [6,1] => ([(0,6),(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[[.,.],.],[[[.,.],.],.]]] => [5,6,7,2,3,4,1] => [6,1] => ([(0,6),(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[[[.,.],.],.],[[.,.],.]]] => [6,7,2,3,4,5,1] => [6,1] => ([(0,6),(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[[[[.,.],.],.],.],[.,.]]] => [7,2,3,4,5,6,1] => [6,1] => ([(0,6),(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[.,[.,[[[.,.],.],.]]],.]] => [4,5,6,3,2,7,1] => [4,1,2] => ([(1,5),(1,6),(2,5),(2,6),(3,5),(3,6),(4,5),(4,6),(5,6)],7) => 0
[.,[[.,[[.,.],[[.,.],.]]],.]] => [5,6,3,4,2,7,1] => [4,1,2] => ([(1,5),(1,6),(2,5),(2,6),(3,5),(3,6),(4,5),(4,6),(5,6)],7) => 0
[.,[[.,[[[[.,.],.],.],.]],.]] => [3,4,5,6,2,7,1] => [5,2] => ([(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[[.,.],[[[.,.],.],.]],.]] => [4,5,6,2,3,7,1] => [5,2] => ([(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[[[.,.],.],[[.,.],.]],.]] => [5,6,2,3,4,7,1] => [5,2] => ([(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[[[[.,.],.],.],[.,.]],.]] => [6,2,3,4,5,7,1] => [5,2] => ([(1,6),(2,6),(3,6),(4,6),(5,6)],7) => 0
[.,[[[.,[.,[[.,.],.]]],.],.]] => [4,5,3,2,6,7,1] => [3,1,3] => ([(2,5),(2,6),(3,5),(3,6),(4,5),(4,6),(5,6)],7) => 0
[.,[[[.,[[[.,.],.],.]],.],.]] => [3,4,5,2,6,7,1] => [4,3] => ([(2,6),(3,6),(4,6),(5,6)],7) => 0
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Description
The second largest eigenvalue of a graph if it is integral.
This statistic is undefined if the second largest eigenvalue of the graph is not integral.
Chapter 4 of [1] provides lots of context.
This statistic is undefined if the second largest eigenvalue of the graph is not integral.
Chapter 4 of [1] provides lots of context.
Map
to threshold graph
Description
The threshold graph corresponding to the composition.
A threshold graph is a graph that can be obtained from the empty graph by adding successively isolated and dominating vertices.
A threshold graph is uniquely determined by its degree sequence.
The Laplacian spectrum of a threshold graph is integral. Interpreting it as an integer partition, it is the conjugate of the partition given by its degree sequence.
A threshold graph is a graph that can be obtained from the empty graph by adding successively isolated and dominating vertices.
A threshold graph is uniquely determined by its degree sequence.
The Laplacian spectrum of a threshold graph is integral. Interpreting it as an integer partition, it is the conjugate of the partition given by its degree sequence.
Map
to 132-avoiding permutation
Description
Return a 132-avoiding permutation corresponding to a binary tree.
The linear extensions of a binary tree form an interval of the weak order called the Sylvester class of the tree. This permutation is the maximal element of the Sylvester class.
The linear extensions of a binary tree form an interval of the weak order called the Sylvester class of the tree. This permutation is the maximal element of the Sylvester class.
Map
DEX composition
Description
The DEX composition of a permutation.
Let $\pi$ be a permutation in $\mathfrak S_n$. Let $\bar\pi$ be the word in the ordered set $\bar 1 < \dots < \bar n < 1 \dots < n$ obtained from $\pi$ by replacing every excedance $\pi(i) > i$ by $\overline{\pi(i)}$. Then the DEX set of $\pi$ is the set of indices $1 \leq i < n$ such that $\bar\pi(i) > \bar\pi(i+1)$. Finally, the DEX composition $c_1, \dots, c_k$ of $n$ corresponds to the DEX subset $\{c_1, c_1 + c_2, \dots, c_1 + \dots + c_{k-1}\}$.
The (quasi)symmetric function
$$ \sum_{\pi\in\mathfrak S_{\lambda, j}} F_{DEX(\pi)}, $$
where the sum is over the set of permutations of cycle type $\lambda$ with $j$ excedances, is the Eulerian quasisymmetric function.
Let $\pi$ be a permutation in $\mathfrak S_n$. Let $\bar\pi$ be the word in the ordered set $\bar 1 < \dots < \bar n < 1 \dots < n$ obtained from $\pi$ by replacing every excedance $\pi(i) > i$ by $\overline{\pi(i)}$. Then the DEX set of $\pi$ is the set of indices $1 \leq i < n$ such that $\bar\pi(i) > \bar\pi(i+1)$. Finally, the DEX composition $c_1, \dots, c_k$ of $n$ corresponds to the DEX subset $\{c_1, c_1 + c_2, \dots, c_1 + \dots + c_{k-1}\}$.
The (quasi)symmetric function
$$ \sum_{\pi\in\mathfrak S_{\lambda, j}} F_{DEX(\pi)}, $$
where the sum is over the set of permutations of cycle type $\lambda$ with $j$ excedances, is the Eulerian quasisymmetric function.
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