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

Terms

a(0) =0a(1) =4096a(2) =65536a(3) =331776a(4) =1048576a(5) =2560000a(6) =5308416a(7) =9834496a(8) =16777216a(9) =26873856a(10) =40960000a(11) =59969536a(12) =84934656a(13) =116985856a(14) =157351936a(15) =207360000a(16) =268435456a(17) =342102016a(18) =429981696a(19) =533794816a(20) =655360000a(21) =796594176a(22) =959512576a(23) =1146228736a(24) =1358954496a(25) =1600000000