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

Terms

a(0) =256a(1) =14641a(2) =104976a(3) =390625a(4) =1048576a(5) =2313441a(6) =4477456a(7) =7890481a(8) =12960000a(9) =20151121a(10) =29986576a(11) =43046721a(12) =59969536a(13) =81450625a(14) =108243216a(15) =141158161a(16) =181063936a(17) =228886641a(18) =285610000a(19) =352275361a(20) =429981696a(21) =519885601a(22) =623201296a(23) =741200625a(24) =875213056a(25) =1026625681