Triangle of numbers related to rooted trees and unrooted planar trees.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =9a(5) =9a(6) =6a(7) =44a(8) =96a(9) =64a(10) =24a(11) =250a(12) =875a(13) =1250a(14) =625a(15) =120a(16) =1644a(17) =8100a(18) =18360a(19) =19440a(20) =7776a(21) =720a(22) =12348a(23) =79576a(24) =252105a(25) =420175a(26) =352947a(27) =117649a(28) =5040a(29) =104544