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 A331883 #18 Feb 12 2020 08:20:49 %S A331883 0,1,1,5,26,132,834,6477,56242 %N A331883 The number of permutations in the symmetric group S_n in which it is possible to find two disjoint increasing subsequences each with length equal to the length of the longest increasing subsequence of the permutation. %C A331883 Only permutations whose longest increasing subsequence is at most n/2 need to be considered. %H A331883 Wikipedia, <a href="https://en.wikipedia.org/wiki/Longest_increasing_subsequence_problem">Longest increasing subsequence problem</a> %e A331883 a(3) = 1 because the only permutation whose longest increasing subsequence is 1 is [3,2,1] and this contains two disjoint increasing subsequences of length 1. %e A331883 The a(4) = 5 permutations are: %e A331883 [2,1,4,3], %e A331883 [2,4,1,3], %e A331883 [3,1,4,2], %e A331883 [3,4,1,2], %e A331883 [4,3,2,1]. %Y A331883 Cf. A047874, A047887, A167995. %K A331883 nonn,more %O A331883 1,4 %A A331883 _Ildar Gainullin_, Jan 30 2020