a(n) = n*a(n-1) + n^(1+n mod 2), a(0) = 0.

Terms

a(0) =0a(1) =1a(2) =4a(3) =13a(4) =56a(5) =281a(6) =1692a(7) =11845a(8) =94768a(9) =852913a(10) =8529140a(11) =93820541a(12) =1125846504a(13) =14636004553a(14) =204904063756