a(n) = n*(n+1)*(3*n^2+5*n+4)/12.

Terms

a(0) =0a(1) =2a(2) =13a(3) =46a(4) =120a(5) =260a(6) =497a(7) =868a(8) =1416a(9) =2190a(10) =3245a(11) =4642a(12) =6448a(13) =8736a(14) =11585a(15) =15080a(16) =19312a(17) =24378a(18) =30381a(19) =37430a(20) =45640a(21) =55132a(22) =66033a(23) =78476a(24) =92600a(25) =108550a(26) =126477a(27) =146538a(28) =168896a(29) =193720