a(n) = (n-1)*(n-2)*(n^2+9*n+12)/24.

Terms

a(0) =1a(1) =0a(2) =0a(3) =4a(4) =16a(5) =41a(6) =85a(7) =155a(8) =259a(9) =406a(10) =606a(11) =870a(12) =1210a(13) =1639a(14) =2171a(15) =2821a(16) =3605a(17) =4540a(18) =5644a(19) =6936a(20) =8436a(21) =10165a(22) =12145a(23) =14399a(24) =16951a(25) =19826a(26) =23050a(27) =26650a(28) =30654a(29) =35091