Number of tree-rooted planar maps with 4 faces and n vertices and no isthmuses.

Terms

a(0) =5a(1) =84a(2) =650a(3) =3324a(4) =13020a(5) =42240a(6) =118998a(7) =300300a(8) =693693a(9) =1490060a(10) =3011580a(11) =5779592a(12) =10608000a(13) =18728832a(14) =31957620a(15) =52907400a(16) =85261341a(17) =134115300a(18) =206402966a(19) =311417700a(20) =461446700a(21) =672534720a(22) =965396250a(23) =1366496820a(24) =1909325925a(25) =2635885980a(26) =3598423704a(27) =4861432400a(28) =6503955744a(29) =8622225920