Number of nonseparable tree-rooted planar maps with n + 2 edges and 3 vertices.

Terms

a(0) =3a(1) =20a(2) =75a(3) =210a(4) =490a(5) =1008a(6) =1890a(7) =3300a(8) =5445a(9) =8580a(10) =13013a(11) =19110a(12) =27300a(13) =38080a(14) =52020a(15) =69768a(16) =92055a(17) =119700a(18) =153615a(19) =194810a(20) =244398a(21) =303600a(22) =373750a(23) =456300a(24) =552825a(25) =665028a(26) =794745a(27) =943950a(28) =1114760a(29) =1309440