a(n) = (7*n + 2)^4.

Terms

a(0) =16a(1) =6561a(2) =65536a(3) =279841a(4) =810000a(5) =1874161a(6) =3748096a(7) =6765201a(8) =11316496a(9) =17850625a(10) =26873856a(11) =38950081a(12) =54700816a(13) =74805201a(14) =100000000a(15) =131079601a(16) =168896016a(17) =214358881a(18) =268435456a(19) =332150625a(20) =406586896a(21) =492884401a(22) =592240896a(23) =705911761a(24) =835210000a(25) =981506241a(26) =1146228736a(27) =1330863361