a(n) = A002467(n) - 1.

Terms

a(0) =0a(1) =0a(2) =3a(3) =14a(4) =75a(5) =454a(6) =3185a(7) =25486a(8) =229383a(9) =2293838a(10) =25232229a(11) =302786758a(12) =3936227867a(13) =55107190150a(14) =826607852265