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A007855
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Infima closed sets in rooted plane trees on n nodes.
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0
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1, 3, 13, 63, 326, 1769, 9964, 57843, 344203, 2090470, 12912988, 80899801, 512896540, 3284651548, 21217493460, 138080484819, 904454380446, 5958186674879, 39448465279220, 262359379484522, 1751912981641794, 11741044418866476
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OFFSET
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1,2
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LINKS
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FORMULA
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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
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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