a(n) = 6^n + n^6.

Terms

a(0) =1a(1) =7a(2) =100a(3) =945a(4) =5392a(5) =23401a(6) =93312a(7) =397585a(8) =1941760a(9) =10609137a(10) =61466176a(11) =364568617a(12) =2179768320a(13) =13065520825a(14) =78371693632a(15) =470196375201