a(n) = (8*n + 5)^4.

Terms

a(0) =625a(1) =28561a(2) =194481a(3) =707281a(4) =1874161a(5) =4100625a(6) =7890481a(7) =13845841a(8) =22667121a(9) =35153041a(10) =52200625a(11) =74805201a(12) =104060401a(13) =141158161a(14) =187388721a(15) =244140625a(16) =312900721a(17) =395254161a(18) =492884401a(19) =607573201