a(n) = A000404(n)^4.

Terms

a(0) =16a(1) =625a(2) =4096a(3) =10000a(4) =28561a(5) =83521a(6) =104976a(7) =160000a(8) =390625a(9) =456976a(10) =707281a(11) =1048576a(12) =1336336a(13) =1874161a(14) =2560000a(15) =2825761a(16) =4100625a(17) =6250000a(18) =7311616a(19) =7890481a(20) =11316496a(21) =13845841a(22) =17850625a(23) =21381376a(24) =26873856a(25) =28398241a(26) =29986576