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

Terms

a(0) =1a(1) =625a(2) =6561a(3) =28561a(4) =83521a(5) =194481a(6) =390625a(7) =707281a(8) =1185921a(9) =1874161a(10) =2825761a(11) =4100625a(12) =5764801a(13) =7890481a(14) =10556001a(15) =13845841a(16) =17850625a(17) =22667121a(18) =28398241a(19) =35153041a(20) =43046721a(21) =52200625a(22) =62742241a(23) =74805201a(24) =88529281a(25) =104060401a(26) =121550625a(27) =141158161a(28) =163047361