a(n) = n! - n^4.

Terms

a(0) =1a(1) =0a(2) =-14a(3) =-75a(4) =-232a(5) =-505a(6) =-576a(7) =2639a(8) =36224a(9) =356319a(10) =3618800a(11) =39902159a(12) =478980864a(13) =6226992239a(14) =87178252784