Column 1 of triangle A115080.

Terms

a(0) =1a(1) =2a(2) =5a(3) =20a(4) =94a(5) =507a(6) =3009a(7) =19350a(8) =132920a(9) =966962a(10) =7396366a(11) =59173897a(12) =492995320a(13) =4262193275a(14) =38125138575a(15) =351960913470