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A002803
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(2n+4)!/(4!n!(n+1)!).
(Formerly M4980 N2140)
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3
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1, 15, 140, 1050, 6930, 42042, 240240, 1312740, 6928350, 35565530, 178474296, 878850700, 4259045700, 20359174500, 96172862400, 449608131720, 2082743551350, 9569730173850, 43651400793000, 197809768856700
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| C. Jordan, Calculus of Finite Differences. Budapest, 1939, p. 449.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Walsh, T. R. S.; Lehman, A. B.; Counting rooted maps by genus. III: Nonseparable maps. J. Combinatorial Theory Ser. B 18 (1975), 222-259.
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LINKS
| T. D. Noe, Table of n, a(n) for n = 0..200
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MAPLE
| seq(binomial(2*i, i)*binomial(i, i-2)*i/12, i=2..21); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 06 2007
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MATHEMATICA
| Table[(2*n+4)!/(4!*n!*(n+1)!), {n, 0, 20}] [From Vladimir Orlovsky, Dec 13 2008]
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CROSSREFS
| Sequence in context: A027802 A133716 A035330 * A056281 A000481 A055903
Adjacent sequences: A002800 A002801 A002802 * A002804 A002805 A002806
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 17 2003
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