a(n) = n*(n+1)*(n^2 + n + 4)/4.

Terms

a(0) =0a(1) =3a(2) =15a(3) =48a(4) =120a(5) =255a(6) =483a(7) =840a(8) =1368a(9) =2115a(10) =3135a(11) =4488a(12) =6240a(13) =8463a(14) =11235a(15) =14640a(16) =18768a(17) =23715a(18) =29583a(19) =36480a(20) =44520a(21) =53823a(22) =64515a(23) =76728a(24) =90600a(25) =106275a(26) =123903a(27) =143640a(28) =165648a(29) =190095