

A112946


Number of unrooted regular oddvalent planar maps with 6 vertices; maps are considered up to orientationpreserving homeomorphisms and the vertices are of valency 2n+1.


3



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

0,2


COMMENTS

There is a closed formula.


LINKS

Table of n, a(n) for n=0..9.
Z. C. Gao, V. A. Liskovets and N. C. Wormald, Enumeration of unrooted oddvalent regular planar maps, Preprint, 2005.


MATHEMATICA

a[n_] := With[{b = Binomial[2n, n]}, (1/120)(36n1) 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] (* JeanFrançois Alcover, Sep 01 2019 *)


CROSSREFS

Cf. A112945, A112947.
Sequence in context: A316677 A092212 A265959 * A034246 A145336 A271246
Adjacent sequences: A112943 A112944 A112945 * A112947 A112948 A112949


KEYWORD

nonn


AUTHOR

Valery A. Liskovets, Oct 10 2005


STATUS

approved



