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A006420
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Number of rooted planar maps with 3 vertices and n faces and no isthmuses.
(Formerly M5012)
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2
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1, 16, 150, 1104, 7077, 41504, 228810, 1205520, 6135690, 30391520, 147277676, 700990752, 3286733805, 15215673408, 69675615234, 316058238864, 1421891923038, 6350464644960, 28179908990772, 124327908683616, 545691921346146, 2383936774151616, 10370479696102500
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OFFSET
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2,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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G.f.: x^2*(1 + 2*g - 4*g^2)/((1 - g)^4*(1 - 2*g)^5)) where g/x is the g.f. of A000108.
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PROG
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(PARI) seq(n)={my(g=x*(1-sqrt(1-4*x + O(x^n)))/(2*x)); Vec((1 + 2*g - 4*g^2)/((1 - g)^4*(1 - 2*g)^5))} \\ Andrew Howroyd, Apr 06 2021
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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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