Number of partition-type permutations in S_n.

Terms

a(0) =1a(1) =2a(2) =4a(3) =13a(4) =36a(5) =126a(6) =428a(7) =1681a(8) =6820a(9) =29233a(10) =127865a(11) =592604a(12) =2829477a(13) =14118079a(14) =72122117a(15) =380843081a(16) =2056927326a(17) =11444517369a(18) =65234523659a(19) =380644223976