a(n) = 6^n-n^8.

Terms

a(0) =1a(1) =5a(2) =-220a(3) =-6345a(4) =-64240a(5) =-382849a(6) =-1632960a(7) =-5484865a(8) =-15097600a(9) =-32969025a(10) =-39533824a(11) =148438175a(12) =1746800640a(13) =12244963295a(14) =76888375040a(15) =467622093951