a(n) = (7*n + 5)^6.

Terms

a(0) =15625a(1) =2985984a(2) =47045881a(3) =308915776a(4) =1291467969a(5) =4096000000a(6) =10779215329a(7) =24794911296a(8) =51520374361a(9) =98867482624a(10) =177978515625a(11) =304006671424a(12) =496981290961a(13) =782757789696