a(n) = 8^n - n^5.

Terms

a(0) =1a(1) =7a(2) =32a(3) =269a(4) =3072a(5) =29643a(6) =254368a(7) =2080345a(8) =16744448a(9) =134158679a(10) =1073641824a(11) =8589773541a(12) =68719227904a(13) =549755442595