Triangle, A000110 in every column > 0, shifted down twice.

Terms

a(0) =1a(1) =1a(2) =2a(3) =1a(4) =5a(5) =1a(6) =15a(7) =2a(8) =1a(9) =52a(10) =5a(11) =1a(12) =203a(13) =15a(14) =2a(15) =1a(16) =877a(17) =52a(18) =5a(19) =1a(20) =4140a(21) =203a(22) =15a(23) =2a(24) =1a(25) =21147a(26) =877a(27) =52a(28) =5a(29) =1