Triangle read by rows, T(n,m) = (1/n)*Sum_{i=1..n} C(n,i-1)*C(n,i)*C(n,m+1-i), T(0,0)=0, m<2n.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =3a(5) =3a(6) =1a(7) =1a(8) =6a(9) =13a(10) =13a(11) =6a(12) =1a(13) =1a(14) =10a(15) =36a(16) =65a(17) =65a(18) =36a(19) =10a(20) =1a(21) =1a(22) =15a(23) =80a(24) =220a(25) =356a(26) =356a(27) =220a(28) =80a(29) =15