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

Terms

a(0) =0a(1) =1a(2) =6a(3) =22a(4) =60a(5) =135a(6) =266a(7) =476a(8) =792a(9) =1245a(10) =1870a(11) =2706a(12) =3796a(13) =5187a(14) =6930a(15) =9080a(16) =11696a(17) =14841a(18) =18582a(19) =22990a(20) =28140a(21) =34111a(22) =40986a(23) =48852a(24) =57800a(25) =67925a(26) =79326a(27) =92106a(28) =106372a(29) =122235