Number of 2-face-free maps on n edges.

Terms

a(0) =0a(1) =2a(2) =6a(3) =23a(4) =90a(5) =372a(6) =1594a(7) =7042a(8) =31888a(9) =147402a(10) =693298a(11) =3309625a(12) =16003002a(13) =78248534a(14) =386383508a(15) =1924611467a(16) =9661445944a(17) =48839412404a(18) =248446494564