a(n) = 1^n + 2^n + ... + 6^n.

Terms

a(0) =6a(1) =21a(2) =91a(3) =441a(4) =2275a(5) =12201a(6) =67171a(7) =376761a(8) =2142595a(9) =12313161a(10) =71340451a(11) =415998681a(12) =2438235715a(13) =14350108521a(14) =84740914531a(15) =501790686201