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%I #13 Dec 27 2018 03:13:24
%S 1,1,2,6,24,120,698,4393,28551,187403,1231517,8080058,52905865,
%T 345820994
%N Number of 2-stack pushall sortable permutations of length n.
%C 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 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 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 Cf. A263929 (permutations sortable with two stacks in series).
%Y Cf. A274969 (pushall stack words of length 3n).
%K nonn,more
%O 0,3
%A _David Bevan_, Jul 13 2016
%E a(11)-a(13) from _Bert Dobbelaere_, Dec 26 2018
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