%I #26 Jul 17 2017 02:24:17
%S 1,2,6,24,120,718,4956,38180,319280,2837959
%N Number of multiplicity free permutations in S_n, i.e., permutations whose Stanley symmetric function is multiplicity free.
%C This family is conjectured to be characterized by a finite set of patterns up to S_11.
%H S. Billey and B. Pawlowski, <a href="https://arxiv.org/abs/1304.7870">Permutation Patterns, Stanley symmetric functions and generalized Specht modules</a>, arXiv:1304.7870 [math.CO], 2013.
%Y Cf. A005802, A223905, A224318.
%K nonn,more
%O 1,2
%A _Sara Billey_, Apr 04 2013