Number of achiral combinatorial maps with n edges.

Terms

a(0) =2a(1) =5a(2) =20a(3) =85a(4) =418a(5) =2242a(6) =12828a(7) =77777a(8) =493286a(9) =3260485a(10) =22314484a(11) =157735801a(12) =1147285362a(13) =8570960234a(14) =65611620808a(15) =513963377327