a(n) = 5^n + n^5.

Terms

a(0) =1a(1) =6a(2) =57a(3) =368a(4) =1649a(5) =6250a(6) =23401a(7) =94932a(8) =423393a(9) =2012174a(10) =9865625a(11) =48989176a(12) =244389457a(13) =1221074418a(14) =6104053449a(15) =30518337500a(16) =152588939201a(17) =762940872982