Triangular array formed by the little Schröder numbers s(n,k).

Terms

a(0) =1a(1) =3a(2) =1a(3) =11a(4) =6a(5) =1a(6) =45a(7) =31a(8) =9a(9) =1a(10) =197a(11) =156a(12) =60a(13) =12a(14) =1a(15) =903a(16) =785a(17) =360a(18) =98a(19) =15a(20) =1a(21) =4279a(22) =3978a(23) =2061a(24) =684a(25) =145a(26) =18a(27) =1a(28) =20793a(29) =20335