a(n) = (8*n + 4)^6.

Terms

a(0) =4096a(1) =2985984a(2) =64000000a(3) =481890304a(4) =2176782336a(5) =7256313856a(6) =19770609664a(7) =46656000000a(8) =98867482624a(9) =192699928576a(10) =351298031616a(11) =606355001344a(12) =1000000000000