a(n) = (n*A003500(n) - A231896(n))/2.

Terms

a(0) =0a(1) =2a(2) =16a(3) =92a(4) =464a(5) =2182a(6) =9824a(7) =42936a(8) =183648a(9) =772746a(10) =3209968a(11) =13196564a(12) =53791408a(13) =217700110a(14) =875718080a(15) =3504277360a(16) =13959102912a(17) =55383875346a(18) =218965651152a(19) =862983998924