Number of permutations divided by the number of (binary) heaps on n elements.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =8a(5) =15a(6) =36a(7) =63a(8) =192a(9) =405a(10) =1080a(11) =2079a(12) =6048a(13) =12285a(14) =31752a(15) =59535a(16) =193536a(17) =433755a(18) =1224720a(19) =2488563a(20) =7620480a(21) =16253055a(22) =44008272a(23) =86266215a(24) =274337280a(25) =602791875a(26) =1671742800a(27) =3341878155a(28) =10081895040a(29) =21210236775