Number of achiral planar maps with n vertices and 2 faces.

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =28a(5) =68a(6) =157a(7) =372a(8) =845a(9) =1949a(10) =4367a(11) =9880a(12) =21858a(13) =48679a(14) =106612a(15) =234546a(16) =509246a(17) =1109352a(18) =2391299a(19) =5167423a(20) =11070598a(21) =23762557a(22) =50641725a(23) =108085708a(24) =229303142a(25) =487039228a(26) =1029167119a(27) =2176808877a(28) =4583856878a(29) =9660020146