One half of binomial coefficients C(2*n-4,5).

Terms

a(0) =3a(1) =28a(2) =126a(3) =396a(4) =1001a(5) =2184a(6) =4284a(7) =7752a(8) =13167a(9) =21252a(10) =32890a(11) =49140a(12) =71253a(13) =100688a(14) =139128a(15) =188496a(16) =250971a(17) =329004a(18) =425334a(19) =543004a(20) =685377a(21) =856152a(22) =1059380a(23) =1299480a(24) =1581255a(25) =1909908a(26) =2291058a(27) =2730756a(28) =3235501a(29) =3812256