a(n) = (2*n^4 - 6*(-1)^n*n^2 - 2*n^2 + 3*(-1)^n - 3)/96.

Terms

a(0) =0a(1) =0a(2) =0a(3) =2a(4) =4a(5) =14a(6) =24a(7) =52a(8) =80a(9) =140a(10) =200a(11) =310a(12) =420a(13) =602a(14) =784a(15) =1064a(16) =1344a(17) =1752a(18) =2160a(19) =2730a(20) =3300a(21) =4070a(22) =4840a(23) =5852a(24) =6864a(25) =8164a(26) =9464a(27) =11102a(28) =12740a(29) =14770