a(n) = n*(n-1)*(n+1)*(3*n-2)/12.

Terms

a(0) =0a(1) =2a(2) =14a(3) =50a(4) =130a(5) =280a(6) =532a(7) =924a(8) =1500a(9) =2310a(10) =3410a(11) =4862a(12) =6734a(13) =9100a(14) =12040a(15) =15640a(16) =19992a(17) =25194a(18) =31350a(19) =38570a(20) =46970a(21) =56672a(22) =67804a(23) =80500a(24) =94900a(25) =111150a(26) =129402a(27) =149814a(28) =172550a(29) =197780