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A007855 Infima closed sets in rooted plane trees on n nodes. 0
1, 3, 13, 63, 326, 1769, 9964, 57843, 344203, 2090470, 12912988, 80899801, 512896540, 3284651548, 21217493460, 138080484819, 904454380446, 5958186674879, 39448465279220, 262359379484522, 1751912981641794, 11741044418866476 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..22.

M. Klazar, Twelve countings with rooted plane trees, European Journal of Combinatorics 18 (1997), 195-210; Addendum, 18 (1997), 739-740.

Index entries for sequences related to rooted trees

FORMULA

G.f.: (1/4) * (1 + sqrt(1-4*x)) * (1 - sqrt(3 - 2 / sqrt(1-4*x))) [from Klazar]. - Sean A. Irvine, Feb 06 2018

CROSSREFS

Sequence in context: A130525 A243280 A000259 * A193112 A192729 A284716

Adjacent sequences:  A007852 A007853 A007854 * A007856 A007857 A007858

KEYWORD

nonn

AUTHOR

Martin Klazar (klazar(AT)kam.mff.cuni.cz)

EXTENSIONS

More terms from Sean A. Irvine, Feb 06 2018

STATUS

approved

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Last modified October 19 05:46 EDT 2018. Contains 316336 sequences. (Running on oeis4.)