a(n) = n*(n + 1)*(n^2 - 3*n + 5)/6.

Terms

a(0) =0a(1) =1a(2) =3a(3) =10a(4) =30a(5) =75a(6) =161a(7) =308a(8) =540a(9) =885a(10) =1375a(11) =2046a(12) =2938a(13) =4095a(14) =5565a(15) =7400a(16) =9656a(17) =12393a(18) =15675a(19) =19570a(20) =24150a(21) =29491a(22) =35673a(23) =42780a(24) =50900a(25) =60125a(26) =70551a(27) =82278a(28) =95410a(29) =110055