Triangle T(n,k) read by rows; related to number of preorders.

Terms

a(0) =1a(1) =1a(2) =4a(3) =4a(4) =1a(5) =15a(6) =63a(7) =96a(8) =48a(9) =1a(10) =44a(11) =468a(12) =1936a(13) =3688a(14) =3264a(15) =1088a(16) =1a(17) =120a(18) =2795a(19) =23990a(20) =98275a(21) =214640a(22) =256720a(23) =158720a(24) =39680