Triangle read by rows: T(n,k)=(1/2)*C(n+k,k)*C(n,n-k).

Terms

a(0) =1a(1) =3a(2) =3a(3) =6a(4) =15a(5) =10a(6) =10a(7) =45a(8) =70a(9) =35a(10) =15a(11) =105a(12) =280a(13) =315a(14) =126a(15) =21a(16) =210a(17) =840a(18) =1575a(19) =1386a(20) =462a(21) =28a(22) =378a(23) =2100a(24) =5775a(25) =8316a(26) =6006a(27) =1716a(28) =36a(29) =630