This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A298248 #45 Feb 26 2024 19:38:23
%S A298248 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,
%T A298248 212,140,212,42,35,0,1,1,0,56,112,675,880,1592,880,675,112,56,0,1,1,0,
%U A298248 84,252,1845,3962,9246,9540,9246,3962,1845,252,84,0,1
%N A298248 Triangle of double-Eulerian numbers DE(n,k) (n >= 0, 0 <= k <= max(0, 2*(n-1))) read by rows.
%C A298248 DE(n,k) = number of permutations with d descents and e descents of the inverse such that d+e = k.
%D A298248 Christian Stump, On bijections between 231-avoiding permutations and Dyck paths, MathSciNet:2734176
%H A298248 Dominique Foata and Guo-Niu Han, <a href="http://irma.math.unistra.fr/~guoniu/papers/index.html">The q-series in Combinatorics; permutation statistics</a>
%H A298248 FindStat - Combinatorial Statistic Finder, <a href="http://www.findstat.org/StatisticsDatabase/St000824/">The sum of the number of descents and the number of recoils of a permutation</a>
%e A298248 The triangle DE(n, k) begins:
%e A298248 n\k 0 1 2 3 4 5 6 7 8 9 10
%e A298248 0: 1
%e A298248 1: 1
%e A298248 2: 1 0 1
%e A298248 3: 1 0 4 0 1
%e A298248 4: 1 0 10 2 10 0 1
%e A298248 5: 1 0 20 12 54 12 20 0 1
%e A298248 6: 1 0 35 42 212 140 212 42 35 0 1
%o A298248 (SageMath)
%o A298248 q = var("q")
%o A298248 [sum( q^(pi.number_of_descents()+pi.inverse().number_of_descents()) for pi in Permutations(n) ).coefficients(sparse=False) for n in [1 .. 6]]
%Y A298248 Row sums give A000142.
%Y A298248 Cf. A000292, A008292, A180389.
%K A298248 nonn,tabf
%O A298248 0,8
%A A298248 _Christian Stump_, Jan 16 2018