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 A112945 Number of unrooted regular odd-valent planar maps with 4 vertices; maps are considered up to orientation-preserving homeomorphisms and the vertices are of valency 2n+1. 3
 0, 6, 468, 80600, 16016560, 3360790440, 728936019504, 161858688461184, 36580777518027600, 8382066029146609800, 1941971956789550319920, 454006489072843947528288, 106944132919124515725427808 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Table of n, a(n) for n=0..12. Z. C. Gao, V. A. Liskovets and N. C. Wormald, Enumeration of unrooted odd-valent regular planar maps, Preprint, 2005; Annals of Combinatorics, August 2009, Volume 13, Issue 2, pp 233-259. FORMULA a(n) = (n/6)*binomial(2n, n)^4+(n/2)*binomial(2n, n)^2+(2/3)*delta(3|(2n+1))* binomial(2*floor(n/3), floor(n/3))*binomial(2n, n) where delta(3|(2n+1))=1 if 3|(2n+1) and =0 otherwise. MATHEMATICA a[n_] := (n/6) Binomial[2n, n]^4 + (n/2) Binomial[2n, n]^2 + (2/3) Boole[ Divisible[2n+1, 3]] Binomial[2 Floor[n/3], Floor[n/3]] Binomial[2n, n]; Table[a[n], {n, 0, 12}] (* Jean-François Alcover, Aug 29 2019 *) CROSSREFS Cf. A112944, A112946. Sequence in context: A024084 A332146 A132590 * A220865 A080295 A084108 Adjacent sequences: A112942 A112943 A112944 * A112946 A112947 A112948 KEYWORD nonn AUTHOR Valery A. Liskovets, Oct 10 2005 STATUS approved

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Last modified September 15 08:13 EDT 2024. Contains 375932 sequences. (Running on oeis4.)