Column 2 of table A125781.

Terms

a(0) =1a(1) =3a(2) =8a(3) =23a(4) =76a(5) =294a(6) =1328a(7) =6933a(8) =41350a(9) =278679a(10) =2101433a(11) =17574551a(12) =161740315a(13) =1626733107a(14) =17771416520a(15) =209739328923