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A007286
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Number of alternating 3-signed permutations.
(Formerly M3945)
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1
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1, 1, 5, 26, 205, 1936, 22265, 297296, 4544185, 78098176, 1491632525, 31336418816, 718181418565, 17831101321216, 476768795646785, 13658417358350336, 417370516232719345, 13551022195053101056
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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REFERENCES
| Richard Ehrenborg and Margaret A. Readdy, Sheffer posets and r-signed permutations, Annales des Sciences Math\'ematiques du Qu\'ebec {\bf 19} (1995), 173-196.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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FORMULA
| G.f.: ( sin x + cos 2x ) / cos 3x.
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CROSSREFS
| Sequence in context: A175151 A121750 A143341 * A099032 A094652 A027529
Adjacent sequences: A007283 A007284 A007285 * A007287 A007288 A007289
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KEYWORD
| nonn
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AUTHOR
| Simon Plouffe (simon.plouffe(AT)gmail.com)
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