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A012028
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E.g.f. sec(sin(arctan(x))) = 1/cos(x/sqrt(1+x^2)).
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0
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1, 1, -7, 121, -3823, 186961, -12464695, 967217161, -51115216735, -15922673810399, 12685061907297305, -7463929930799687399, 4531120544938557395633, -3032728078954072676445839
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OFFSET
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0,3
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LINKS
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FORMULA
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E.g.f.: 1/cos(x/sqrt(1+x^2)) = 1 + x^2/(G(0)) where G(k)= 2*(2*k+1)*(k+1)*(1+x^2) - x^2 + 2*(2*k+1)*(k+1)*x^2*(1+x^2)/G(k+1); (continued fraction, Euler's 1st kind, 1-step). - Sergei N. Gladkovskii, Aug 06 2012
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EXAMPLE
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sec(sin(arctan(x)))=1+1/2!*x^2-7/4!*x^4+121/6!*x^6-3823/8!*x^8...
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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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