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%I #19 Apr 05 2019 10:06:14
%S 1,3,13,63,326,1769,9964,57843,344203,2090470,12912988,80899801,
%T 512896540,3284651548,21217493460,138080484819,904454380446,
%U 5958186674879,39448465279220,262359379484522,1751912981641794,11741044418866476
%N Infima closed sets in rooted plane trees on n nodes.
%H M. Klazar, <a href="http://dx.doi.org/10.1006/eujc.1995.0095">Twelve countings with rooted plane trees</a>, European Journal of Combinatorics 18 (1997), 195-210; Addendum, 18 (1997), 739-740.
%H <a href="/index/Ro#rooted">Index entries for sequences related to rooted trees</a>
%F 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
%o (PARI) my(x='x+O('x^30)); Vec((1/4) * (1+sqrt(1-4*x)) * (1-sqrt(3-2/sqrt(1-4*x)))) \\ _Michel Marcus_, Apr 05 2019
%K nonn
%O 1,2
%A _Martin Klazar_
%E More terms from _Sean A. Irvine_, Feb 06 2018
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