a(n) = (1/2)*floor(n/2)*floor((n-1)/2)*floor((n-2)/2).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =6a(7) =9a(8) =18a(9) =24a(10) =40a(11) =50a(12) =75a(13) =90a(14) =126a(15) =147a(16) =196a(17) =224a(18) =288a(19) =324a(20) =405a(21) =450a(22) =550a(23) =605a(24) =726a(25) =792a(26) =936a(27) =1014a(28) =1183a(29) =1274