a(n) = 2*binomial(n,4).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =2a(5) =10a(6) =30a(7) =70a(8) =140a(9) =252a(10) =420a(11) =660a(12) =990a(13) =1430a(14) =2002a(15) =2730a(16) =3640a(17) =4760a(18) =6120a(19) =7752a(20) =9690a(21) =11970a(22) =14630a(23) =17710a(24) =21252a(25) =25300a(26) =29900a(27) =35100a(28) =40950a(29) =47502