Symmetric triangle read by rows refining A109113.

Terms

a(0) =1a(1) =1a(2) =1a(3) =6a(4) =6a(5) =1a(6) =1a(7) =11a(8) =33a(9) =33a(10) =11a(11) =1a(12) =1a(13) =16a(14) =85a(15) =189a(16) =189a(17) =85a(18) =16a(19) =1a(20) =1a(21) =21a(22) =162a(23) =590a(24) =1107a(25) =1107a(26) =590a(27) =162a(28) =21a(29) =1