

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



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];


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



