a(n) = 5*n^4.

Terms

a(0) =0a(1) =5a(2) =80a(3) =405a(4) =1280a(5) =3125a(6) =6480a(7) =12005a(8) =20480a(9) =32805a(10) =50000a(11) =73205a(12) =103680a(13) =142805a(14) =192080a(15) =253125a(16) =327680a(17) =417605a(18) =524880a(19) =651605a(20) =800000a(21) =972405a(22) =1171280a(23) =1399205a(24) =1658880a(25) =1953125a(26) =2284880a(27) =2657205a(28) =3073280a(29) =3536405