A112946 Number of unrooted regular odd-valent planar maps with 6 vertices; maps are considered up to orientation-preserving homeomorphisms and the vertices are of valency 2n+1.

0, 26, 111096, 513654400, 2243178389200, 9550256850912960, 40141310067406592352, 167483578096089845880576, 695587719666862982630642400, 2880023438585172541459822939200

Offset: 0

Author

Valery A. Liskovets, Oct 10 2005

Keywords

• nonn

Comments

There is a closed formula.

Links

• Z. C. Gao, V. A. Liskovets and N. C. Wormald, Enumeration of unrooted odd-valent regular planar maps, Preprint, 2005.

Crossrefs

Cf. A112945, A112947.

Programs

Mathematica

a[n_] := With[{b = Binomial[2n, n]}, (1/120)(36n-1) n^2 b^6 + (3n^2 b^3)/4 + n b^2/3 + (4/5) Boole[Divisible[2n+1, 5]] Binomial[2 Floor[n/5], Floor[n/5]] b];
a /@ Range[0, 9] (* Jean-François Alcover, Sep 01 2019 *)