Number of unrooted two-vertex (or, dually, two-face) regular planar maps of valency n considered up to orientation-preserving homeomorphism.

A113182

Number of unrooted two-vertex (or, dually, two-face) regular planar maps of valency n considered up to orientation-preserving homeomorphism.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =3a(4) =7a(5) =14a(6) =39a(7) =95a(8) =308a(9) =859a(10) =3013a(11) =9130a(12) =33300a(13) =106039a(14) =394340a(15) =1297295a(16) =4878109a(17) =16428300a(18) =62232321a(19) =213388961a(20) =812825244a(21) =2827645453a(22) =10818489817a(23) =38086408002a(24) =146250545528a(25) =520062618300

External references