A triangle of coefficients: T(n,m) = (2*n + 2*m + 3)! / (2*(2*m + 1)!*(2*n + 1)!).

Terms

a(0) =3a(1) =10a(2) =70a(3) =21a(4) =252a(5) =1386a(6) =36a(7) =660a(8) =5148a(9) =25740a(10) =55a(11) =1430a(12) =15015a(13) =97240a(14) =461890a(15) =78a(16) =2730a(17) =37128a(18) =302328a(19) =1763580a(20) =8112468a(21) =105a(22) =4760a(23) =81396a(24) =813960a(25) =5720330a(26) =31201800a(27) =140408100a(28) =136a(29) =7752