Sum of root degrees of all symmetric ordered trees with n edges.

Terms

a(0) =1a(1) =3a(2) =5a(3) =12a(4) =20a(5) =45a(6) =77a(7) =168a(8) =294a(9) =630a(10) =1122a(11) =2376a(12) =4290a(13) =9009a(14) =16445a(15) =34320a(16) =63206a(17) =131274a(18) =243542a(19) =503880a(20) =940576a(21) =1939938a(22) =3640210a(23) =7488432a(24) =14115100a(25) =28973100a(26) =54826020a(27) =112326480a(28) =213286590a(29) =436268025