A298248 Triangle of double-Eulerian numbers DE(n,k) (n >= 0, 0 <= k <= max(0, 2*(n-1))) read by rows.
1, 1, 1, 0, 1, 1, 0, 4, 0, 1, 1, 0, 10, 2, 10, 0, 1, 1, 0, 20, 12, 54, 12, 20, 0, 1, 1, 0, 35, 42, 212, 140, 212, 42, 35, 0, 1, 1, 0, 56, 112, 675, 880, 1592, 880, 675, 112, 56, 0, 1, 1, 0, 84, 252, 1845, 3962, 9246, 9540, 9246, 3962, 1845, 252, 84, 0, 1
Offset: 0
Examples
The triangle DE(n, k) begins: n\k 0 1 2 3 4 5 6 7 8 9 10 0: 1 1: 1 2: 1 0 1 3: 1 0 4 0 1 4: 1 0 10 2 10 0 1 5: 1 0 20 12 54 12 20 0 1 6: 1 0 35 42 212 140 212 42 35 0 1
References
- Christian Stump, On bijections between 231-avoiding permutations and Dyck paths, MathSciNet:2734176
Links
- Dominique Foata and Guo-Niu Han, The q-series in Combinatorics; permutation statistics
- FindStat - Combinatorial Statistic Finder, The sum of the number of descents and the number of recoils of a permutation
Programs
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SageMath
q = var("q") [sum( q^(pi.number_of_descents()+pi.inverse().number_of_descents()) for pi in Permutations(n) ).coefficients(sparse=False) for n in [1 .. 6]]
Comments