a(n) = n! - n^5.

Terms

a(0) =1a(1) =0a(2) =-30a(3) =-237a(4) =-1000a(5) =-3005a(6) =-7056a(7) =-11767a(8) =7552a(9) =303831a(10) =3528800a(11) =39755749a(12) =478752768a(13) =6226649507a(14) =87177753376