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A005647
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Salié numbers.
(Formerly M3066)
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8
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1, 1, 3, 19, 217, 3961, 105963, 3908059, 190065457, 11785687921, 907546301523, 84965187064099, 9504085749177097, 1251854782837499881, 191781185418766714683, 33810804270120276636139, 6796689405759438360407137, 1545327493049348356667631841
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OFFSET
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0,3
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COMMENTS
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REFERENCES
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L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 87, Problem 32.
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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Expand cosh x / cos x and multiply coefficients by n!/(2^(n/2)).
a(n) ~ (2*n)! * 2^(n+2) * cosh(Pi/2) / Pi^(2*n+1). - Vaclav Kotesovec, Mar 08 2014
G.f.: A(x) = 1/(1 - x/(1 - 2x/(1 - 5x/(1 - 8x/(1 - 13x/(1 - 18x/(1 -...))))))), a continued fraction where the coefficients are A000982 (ceiling(n^2/2)). - Benedict W. J. Irwin, Feb 10 2016
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MATHEMATICA
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nmax = 17; se = Series[ Cosh[x]/Cos[x], {x, 0, 2*nmax}]; a[n_] := Coefficient[se, x, 2*n]*(2*n)!/2^n; Table[a[n], {n, 0, nmax}](* Jean-François Alcover, May 11 2012 *)
Join[{1}, Table[SeriesCoefficient[Series[1/(1+ContinuedFractionK[Floor[(k^2+ 1)/2]*x*-1, 1, {k, 1, 20}]), {x, 0, 20}], n], {n, 1, 20}]](* Benedict W. J. Irwin, Feb 10 2016 *)
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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STATUS
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approved
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