Number of heapable permutations of length n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =17a(6) =71a(7) =359a(8) =2126a(9) =14495a(10) =111921a(11) =966709a(12) =9243208a(13) =96991006a(14) =1108710232a(15) =13719469288a(16) =182771488479