a(n) = Sum_{k<n, k!==0 (mod n)} k!/n.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =0a(5) =25a(6) =0a(7) =738a(8) =5120a(9) =40908a(10) =0a(11) =3662892a(12) =0a(13) =482141160a(14) =6261884552a(15) =87600164760a(16) =0a(18) =0a(22) =0