a(n) = (8*n + 7)^4.

Terms

a(0) =2401a(1) =50625a(2) =279841a(3) =923521a(4) =2313441a(5) =4879681a(6) =9150625a(7) =15752961a(8) =25411681a(9) =38950081a(10) =57289761a(11) =81450625a(12) =112550881a(13) =151807041a(14) =200533921a(15) =260144641a(16) =332150625a(17) =418161601a(18) =519885601a(19) =639128961a(20) =777796321a(21) =937890625a(22) =1121513121a(23) =1330863361a(24) =1568239201a(25) =1836036801