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 A274970 #13 Dec 27 2018 03:13:24 %S A274970 1,1,2,6,24,120,698,4393,28551,187403,1231517,8080058,52905865, %T A274970 345820994 %N A274970 Number of 2-stack pushall sortable permutations of length n. %C A274970 A 2-stack pushall sortable permutation is one that can be sorted by two stacks in series by pushing all elements to the stacks before writing any element to the output. %C A274970 A permutation of length n is 2-stack pushall sortable if and only if it can be sorted by a sequence of 3n operations represented by a pushall stack word of length 3n. %H A274970 Adeline Pierrot and Dominique Rossin, <a href="http://arxiv.org/abs/1303.4376">2-stack pushall sortable permutations</a>, arXiv:1303.4376 [cs.DM], 2013. %Y A274970 Cf. A263929 (permutations sortable with two stacks in series). %Y A274970 Cf. A274969 (pushall stack words of length 3n). %K A274970 nonn,more %O A274970 0,3 %A A274970 _David Bevan_, Jul 13 2016 %E A274970 a(11)-a(13) from _Bert Dobbelaere_, Dec 26 2018