a(n) = (7*n + 1)^4.

Terms

a(0) =1a(1) =4096a(2) =50625a(3) =234256a(4) =707281a(5) =1679616a(6) =3418801a(7) =6250000a(8) =10556001a(9) =16777216a(10) =25411681a(11) =37015056a(12) =52200625a(13) =71639296a(14) =96059601a(15) =126247696a(16) =163047361a(17) =207360000a(18) =260144641a(19) =322417936a(20) =395254161