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

Terms

a(0) =5a(1) =37a(2) =150a(3) =449a(4) =1113a(5) =2422a(6) =4788a(7) =8790a(8) =15213a(9) =25091a(10) =39754a(11) =60879a(12) =90545a(13) =131292a(14) =186184a(15) =258876a(16) =353685a(17) =475665a(18) =630686a(19) =825517a(20) =1067913a(21) =1366706a(22) =1731900a(23) =2174770a(24) =2707965a(25) =3345615a(26) =4103442a(27) =4998875a(28) =6051169a(29) =7281528