Riordan array (f(x), x*f(x)) where f(x) is the g.f. of A033321.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =1a(6) =6a(7) =5a(8) =3a(9) =1a(10) =21a(11) =16a(12) =9a(13) =4a(14) =1a(15) =79a(16) =58a(17) =31a(18) =14a(19) =5a(20) =1a(21) =311a(22) =224a(23) =117a(24) =52a(25) =20a(26) =6a(27) =1a(28) =1265a(29) =900