Number of different 3 against 3 matches given n players.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =10a(7) =70a(8) =280a(9) =840a(10) =2100a(11) =4620a(12) =9240a(13) =17160a(14) =30030a(15) =50050a(16) =80080a(17) =123760a(18) =185640a(19) =271320a(20) =387600a(21) =542640a(22) =746130a(23) =1009470a(24) =1345960a(25) =1771000a(26) =2302300a(27) =2960100a(28) =3767400a(29) =4750200