Number of primitive maps on n edges.

Terms

a(0) =2a(1) =1a(2) =1a(3) =3a(4) =9a(5) =32a(6) =122a(7) =494a(8) =2088a(9) =9130a(10) =41018a(11) =188420a(12) =881718a(13) =4191343a(14) =20194345a(15) =98442879a(16) =484826387a(17) =2409437854a(18) =12070883798a(19) =60910296202a(20) =309356790766