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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. 3
0, 26, 111096, 513654400, 2243178389200, 9550256850912960, 40141310067406592352, 167483578096089845880576, 695587719666862982630642400, 2880023438585172541459822939200 (list; graph; refs; listen; history; text; internal format)
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 odd-valent regular planar maps, Preprint, 2005.

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-Fran├žois 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

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Last modified October 20 16:07 EDT 2021. Contains 348111 sequences. (Running on oeis4.)