a(n) = (10*n + 5)^6.

Terms

a(0) =15625a(1) =11390625a(2) =244140625a(3) =1838265625a(4) =8303765625a(5) =27680640625a(6) =75418890625a(7) =177978515625a(8) =377149515625a(9) =735091890625