Binomial (Binomial (n,2), 3) - Binomial (Binomial (n,3), 2).

Terms

a(0) =0a(1) =1a(2) =14a(3) =75a(4) =265a(5) =735a(6) =1736a(7) =3654a(8) =7050a(9) =12705a(10) =21670a(11) =35321a(12) =55419a(13) =84175a(14) =124320a(15) =179180a(16) =252756a(17) =349809a(18) =475950a(19) =637735a(20) =842765a(21) =1099791a(22) =1418824a(23) =1811250a(24) =2289950a(25) =2869425a(26) =3565926a(27) =4397589a(28) =5384575a(29) =6549215