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A007289
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Number of alternating 3-signed permutations.
(Formerly M1873)
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3
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1, 2, 8, 46, 352, 3362, 38528, 515086, 7869952, 135274562, 2583554048, 54276473326, 1243925143552, 30884386347362, 825787662368768, 23657073914466766, 722906928498737152, 23471059057478981762
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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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
| E.g.f.: (sin(2*x) + cos(x)) / cos(3*x).
a(n) = Sum_{k=0..n} Sum_{j=0..k} (-1)^j*binomial(k,j)*(k-2*j)^n*I^(n-k). [Peter Luschny, Jul 31 2011]
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MAPLE
| A007289 := proc(n) local k, j; add(add((-1)^j*binomial(k, j)*(k-2*j)^n*I^(n-k), j=0..k), k=0..n) end: [Peter Luschny, Jul 31 2011]
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CROSSREFS
| Sequence in context: A052801 A180390 A074599 * A099765 A096656 A102009
Adjacent sequences: A007286 A007287 A007288 * A007290 A007291 A007292
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
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