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

Terms

a(0) =0a(1) =1a(2) =9a(3) =10a(4) =50a(5) =35a(6) =147a(7) =84a(8) =324a(9) =165a(10) =605a(11) =286a(12) =1014a(13) =455a(14) =1575a(15) =680a(16) =2312a(17) =969a(18) =3249a(19) =1330a(20) =4410a(21) =1771a(22) =5819a(23) =2300a(24) =7500a(25) =2925a(26) =9477a(27) =3654a(28) =11774a(29) =4495