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

Terms

a(0) =0a(1) =3a(2) =10a(3) =23a(4) =44a(5) =75a(6) =118a(7) =175a(8) =248a(9) =339a(10) =450a(11) =583a(12) =740a(13) =923a(14) =1134a(15) =1375a(16) =1648a(17) =1955a(18) =2298a(19) =2679a(20) =3100a(21) =3563a(22) =4070a(23) =4623a(24) =5224a(25) =5875a(26) =6578a(27) =7335a(28) =8148a(29) =9019