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A006408
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Number of nonseparable rooted toroidal maps with n + 3 edges and n + 1 vertices.
(Formerly M3672)
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2
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4, 39, 190, 651, 1792, 4242, 8988, 17490, 31812, 54769, 90090, 142597, 218400, 325108, 472056, 670548, 934116, 1278795, 1723414, 2289903, 3003616, 3893670, 4993300, 6340230, 7977060, 9951669, 12317634, 15134665, 18469056, 22394152, 26990832, 32348008, 38563140
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OFFSET
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2,1
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COMMENTS
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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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a(n) = (n*(12-28*n-45*n^2+20*n^3+33*n^4+8*n^5))/360.
G.f.: -x^2*(x^2 + 11*x + 4) / (x-1)^7. (End)
a(n) = binomial(n+2,4)*(8*n^2 + 17*n - 6)/15. - Andrew Howroyd, Apr 05 2021
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PROG
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(PARI) a(n) = {binomial(n+2, 4)*(8*n^2 + 17*n - 6)/15} \\ Andrew Howroyd, Apr 05 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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