a(n) = A000404(n)^6.

Terms

a(0) =64a(1) =15625a(2) =262144a(3) =1000000a(4) =4826809a(5) =24137569a(6) =34012224a(7) =64000000a(8) =244140625a(9) =308915776a(10) =594823321a(11) =1073741824a(12) =1544804416a(13) =2565726409a(14) =4096000000a(15) =4750104241a(16) =8303765625a(17) =15625000000a(18) =19770609664a(19) =22164361129a(20) =38068692544