a(n) = n*(5*n^2 - 3*n + 4) / 6.

Terms

a(0) =0a(1) =1a(2) =6a(3) =20a(4) =48a(5) =95a(6) =166a(7) =266a(8) =400a(9) =573a(10) =790a(11) =1056a(12) =1376a(13) =1755a(14) =2198a(15) =2710a(16) =3296a(17) =3961a(18) =4710a(19) =5548a(20) =6480a(21) =7511a(22) =8646a(23) =9890a(24) =11248a(25) =12725a(26) =14326a(27) =16056a(28) =17920a(29) =19923