a(n) = n*(n+1)*(2*n+1)*(3*n+1)*(4*n+1)/6.

Terms

a(0) =0a(1) =20a(2) =315a(3) =1820a(4) =6630a(5) =18480a(6) =43225a(7) =89320a(8) =168300a(9) =295260a(10) =489335a(11) =774180a(12) =1178450a(13) =1736280a(14) =2487765a(15) =3479440a(16) =4764760a(17) =6404580a(18) =8467635a(19) =11031020a(20) =14180670a(21) =18011840a(22) =22629585a(23) =28149240a(24) =34696900a(25) =42409900a(26) =51437295a(27) =61940340a(28) =74092970a(29) =88082280