Triangle read by rows: T(n,k)=(n+k)!/k! (0<=k<=n-1; n>=1).

Terms

a(0) =1a(1) =2a(2) =6a(3) =6a(4) =24a(5) =60a(6) =24a(7) =120a(8) =360a(9) =840a(10) =120a(11) =720a(12) =2520a(13) =6720a(14) =15120a(15) =720a(16) =5040a(17) =20160a(18) =60480a(19) =151200a(20) =332640a(21) =5040a(22) =40320a(23) =181440a(24) =604800a(25) =1663200a(26) =3991680a(27) =8648640a(28) =40320a(29) =362880