Triangle enumerating certain two-line arrays of positive integers.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =4a(6) =1a(7) =7a(8) =21a(9) =21a(10) =1a(11) =10a(12) =47a(13) =126a(14) =126a(15) =1a(16) =13a(17) =82a(18) =324a(19) =818a(20) =818a(21) =1a(22) =16a(23) =126a(24) =642a(25) =2300a(26) =5594a(27) =5594a(28) =1a(29) =19