a(n) = n*(n+1)*(5*n+7)/6.

Terms

a(0) =0a(1) =4a(2) =17a(3) =44a(4) =90a(5) =160a(6) =259a(7) =392a(8) =564a(9) =780a(10) =1045a(11) =1364a(12) =1742a(13) =2184a(14) =2695a(15) =3280a(16) =3944a(17) =4692a(18) =5529a(19) =6460a(20) =7490a(21) =8624a(22) =9867a(23) =11224a(24) =12700a(25) =14300a(26) =16029a(27) =17892a(28) =19894a(29) =22040