a(n) = Sum_{k=1..7} n^k.

Terms

a(0) =0a(1) =7a(2) =254a(3) =3279a(4) =21844a(5) =97655a(6) =335922a(7) =960799a(8) =2396744a(9) =5380839a(10) =11111110a(11) =21435887a(12) =39089244a(13) =67977559a(14) =113522234a(15) =183063615a(16) =286331152a(17) =435984839a(18) =648232974a(19) =943531279a(20) =1347368420a(21) =1891142967a(22) =2613136834a(23) =3559590239a(24) =4785883224a(25) =6357828775a(26) =8353082582