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A072477 (2*n)!*binomial(2*n,n)/8. 0
18, 1800, 352800, 114307200, 55324684800, 37399486924800, 33659538232320000, 38910426196561920000, 56186655427835412480000, 99113260174701667614720000, 209723658529668728672747520000, 524309146324171821681868800000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Table of n, a(n) for n=2..13.

Michel Bousquet, Gilbert Labelle and Pierre Leroux, Enumeration of planar 2-face maps, Discrete Mathematics, 222 (2000), 1-25.

CROSSREFS

Sequence in context: A253121 A067303 A055740 * A249332 A019522 A068181

Adjacent sequences:  A072474 A072475 A072476 * A072478 A072479 A072480

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Aug 02 2002

STATUS

approved

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Last modified February 24 11:12 EST 2018. Contains 299603 sequences. (Running on oeis4.)