a(n) = (5*n + 1)^4.

Terms

a(0) =1a(1) =1296a(2) =14641a(3) =65536a(4) =194481a(5) =456976a(6) =923521a(7) =1679616a(8) =2825761a(9) =4477456a(10) =6765201a(11) =9834496a(12) =13845841a(13) =18974736a(14) =25411681a(15) =33362176a(16) =43046721a(17) =54700816a(18) =68574961a(19) =84934656a(20) =104060401a(21) =126247696