%I #11 Sep 14 2012 21:52:37
%S 0,1,1,3,12,56,289,1602,9367,57075,359346,2323416,15356446,103389175,
%T 707107627,4901988047,34384943850,243694702311,1742953208739,
%U 12567593026554,91280392585747,667341975412356,4907899368783645,36289929612761691,269660272111724536,2012845416966620068,15087243969226496324,113521159338891300347,857211201390859034536
%N Number of indecomposable permutations sortable using two parallel stacks.
%C Suggested by _Peter Doyle_ in an email message, Sep 04 2012
%H N. J. A. Sloane, <a href="/A215252/b215252.txt">Table of n, a(n) for n = 0..100</a>
%F INVERTi transform of A216040.
%Y Cf. A003319, A216040, A182216, A215257.
%K nonn
%O 0,4
%A _N. J. A. Sloane_, Sep 07 2012. a(0)=0 added by _N. J. A. Sloane_, Sep 12 2012