Triangle: see Mathematica code.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =1a(7) =2a(8) =3a(9) =6a(10) =1a(11) =3a(12) =40a(13) =35a(14) =24a(15) =1a(16) =4a(17) =165a(18) =8372a(19) =1755a(20) =120a(21) =1a(22) =5a(23) =456a(24) =159831a(25) =17174080a(26) =382075a(27) =720a(28) =1a(29) =6