Second diagonal of A059720.

Terms

a(0) =1a(1) =6a(2) =29a(3) =148a(4) =818a(5) =4964a(6) =32989a(7) =238931a(8) =1875750a(9) =15877954a(10) =144229155a(11) =1399818783a(12) =14459867443a(13) =158421403734