a(n) = (9n+1)^4.

Terms

a(0) =1a(1) =10000a(2) =130321a(3) =614656a(4) =1874161a(5) =4477456a(6) =9150625a(7) =16777216a(8) =28398241a(9) =45212176a(10) =68574961a(11) =100000000a(12) =141158161a(13) =193877776a(14) =260144641a(15) =342102016a(16) =442050625a(17) =562448656a(18) =705911761a(19) =875213056