Main diagonal of table A162430.

Terms

a(0) =1a(1) =3a(2) =13a(3) =76a(4) =535a(5) =3921a(6) =31767a(7) =283574a(8) =2679558a(9) =26954099a(10) =285775908a(11) =3183625080a(12) =37069123612a(13) =449410859046