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Search: id:A002803
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| A002803 |
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(2n+4)!/(4!n!(n+1)!).
(Formerly M4980 N2140)
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+0
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; listen)
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OFFSET
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0,2
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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).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
C. Jordan, Calculus of Finite Differences. Budapest, 1939, p. 449.
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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MAPLE
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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
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a[n_]:=(2*n+4)!/(4!*n!*(n+1)!); [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Dec 13 2008]
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CROSSREFS
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Sequence in context: A027802 A133716 A035330 this_sequence A056281 A000481 A055903
Adjacent sequences: A002800 A002801 A002802 this_sequence A002804 A002805 A002806
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 17 2003
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