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A128274
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Absolute values of numerators of series expansion of cosh(x)/sqrt((cosh(x))^2+(sinh(x))^2) about 0 (even indexed coefficients only).
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1
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1, 1, 17, 721, 58337, 7734241, 218014151, 419784870961, 153563504618177, 10300599833780983, 2486497854930863041, 30262124466958766778001, 3711710439292601861342231, 26350476755161831091778460321, 31166629149666821954776191205937, 45673109693364177065089340171611
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OFFSET
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0,3
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LINKS
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Table of n, a(n) for n=0..15.
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MATHEMATICA
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Series[Cosh[x]/(Sqrt[Cosh[x]^2 + Sinh[x]^2]), {x, 0, 20}]
cc=CoefficientList[Series[Sinh[x]/(Sqrt[Cosh[x]^2+Sinh[x]^2]), {x, -, 26}], x]; kk={}; Do[AppendTo[kk, Abs[Numerator[cc[[k]]]], {k, 2, Length[cc], 2]; kk
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CROSSREFS
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Cf. A012085, A012193.
Sequence in context: A012182 A012029 A012193 * A012085 A298306 A308696
Adjacent sequences: A128271 A128272 A128273 * A128275 A128276 A128277
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski, Feb 22 2007
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EXTENSIONS
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Offset 0 and more terms from Alois P. Heinz, Apr 08 2021
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STATUS
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approved
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