A Galton triangle: T(n,k) = 2*k*T(n-1,k) + (2*k-1)*T(n-1,k-1).

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =18a(5) =15a(6) =8a(7) =84a(8) =180a(9) =105a(10) =16a(11) =360a(12) =1500a(13) =2100a(14) =945a(15) =32a(16) =1488a(17) =10800a(18) =27300a(19) =28350a(20) =10395a(21) =64a(22) =6048a(23) =72240a(24) =294000a(25) =529200a(26) =436590a(27) =135135a(28) =128a(29) =24384