a(n) = binomial(n,4) - binomial(floor(n/2),4) - binomial(ceiling(n/2),4).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =5a(6) =15a(7) =34a(8) =68a(9) =120a(10) =200a(11) =310a(12) =465a(13) =665a(14) =931a(15) =1260a(16) =1680a(17) =2184a(18) =2808a(19) =3540a(20) =4425a(21) =5445a(22) =6655a(23) =8030a(24) =9636a(25) =11440a(26) =13520a(27) =15834a(28) =18473a(29) =21385