Number of 3-ary plane multitrees with n edges.

Terms

a(0) =1a(1) =1a(2) =3a(3) =10a(4) =28a(5) =93a(6) =317a(7) =1090a(8) =3876a(9) =13995a(10) =51182a(11) =189606a(12) =709218a(13) =2675230a(14) =10166639a(15) =38883721a(16) =149559230a(17) =578153160a(18) =2245017535a(19) =8752828951a(20) =34250020397a(21) =134465596581a(22) =529509173245