a(n) = n*(n+1)*(n^2 - 3*n + 6)/4.

Terms

a(0) =0a(1) =2a(2) =6a(3) =18a(4) =50a(5) =120a(6) =252a(7) =476a(8) =828a(9) =1350a(10) =2090a(11) =3102a(12) =4446a(13) =6188a(14) =8400a(15) =11160a(16) =14552a(17) =18666a(18) =23598a(19) =29450a(20) =36330a(21) =44352a(22) =53636a(23) =64308a(24) =76500a(25) =90350a(26) =106002a(27) =123606a(28) =143318a(29) =165300