a(n) = 5n*(5n-1)*(5n-2)*(5n-3)*(5n-4).

Terms

a(0) =0a(1) =120a(2) =30240a(3) =360360a(4) =1860480a(5) =6375600a(6) =17100720a(7) =38955840a(8) =78960960a(9) =146611080a(10) =254251200a(11) =417451320a(12) =655381440a(13) =991186560a(14) =1452361680a(15) =2071126800a(16) =2884801920a(17) =3936182040a(18) =5273912160a(19) =6952862280a(20) =9034502400a(21) =11587277520a(22) =14686982640a(23) =18417137760