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A003702
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Expansion of tan(x)/cosh(x).
(Formerly M5110)
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5
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1, -1, 21, -141, 10441, -183481, 29429661, -987318021, 276117553681, -15085947275761, 6514632269358501, -526614587249608701, 324871912636292700121, -36433570919762397948841, 30417659816002454665514541
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OFFSET
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0,3
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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).
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LINKS
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FORMULA
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a(n) ~ (2*exp(Pi/2) + (exp(Pi) - 1)*(-1)^n) * (2*n+1)! * 2^(2*n+3) / ((1+exp(Pi)) * Pi^(2*n+2)). - Vaclav Kotesovec, Feb 16 2015
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MATHEMATICA
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Tan[ x ]/Cosh[ x ] (* Odd Part *)
nn = 20; Table[(CoefficientList[Series[Sech[x]*Tan[x], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 16 2015 *)
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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