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A012821
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Expansion of e.g.f. exp(sec(x)*arcsinh(x)).
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2
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1, 1, 1, 3, 9, 45, 225, 1071, 6993, 56697, 467745, 3279419, 29529753, 376156261, 4297350785, 35274762407, 378759492257, 8003761282417, 122599030798017, 853554115621363, 8002975063348265, 450081179390735645
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OFFSET
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0,4
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COMMENTS
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The first negative number is a(24) = -686072407102337430543.
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LINKS
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EXAMPLE
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exp(sec(x)*arcsinh(x)) = 1 + x + 1/2!*x^2 + 3/3!*x^3 + 9/4!*x^4 + 45/5!*x^5 + ...
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PROG
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(PARI) seq(n)={my(x='x+O('x^n)); Vec(serlaplace(exp(asinh(x)/cos(x))))} \\ Andrew Howroyd, Feb 25 2018
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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Patrick Demichel (patrick.demichel(AT)hp.com)
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STATUS
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approved
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