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A009011
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Expansion of 1/cos(tanh(x)).
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1
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1, 1, -3, -3, 665, -25031, 607893, 13065717, -3684215119, 322746228337, -2173907680851, -5317484317809939, 1007358319257596489, 46704901267812186793, -111828938184578058229947
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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EXAMPLE
| 1/cos(tanh x) = 1+ 1*x^2/2! -3*x^4/4! -3*x^6/6! +665*x^8/8! -25031*x^10/10! +... = 1 +x^2/2 -x^4/8 -x^6/240 +19*x^8/1152 -25031*x^10/3628800 +...
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MATHEMATICA
| 1/Cos[ Tanh[ x ] ] (* Even Part *)
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CROSSREFS
| Sequence in context: A007301 A009715 A138662 * A009498 A076253 A081174
Adjacent sequences: A009008 A009009 A009010 * A009012 A009013 A009014
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KEYWORD
| sign
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AUTHOR
| R. H. Hardin (rhhardin(AT)att.net)
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EXTENSIONS
| Extended with signs Mar 15 1997 by Olivier Gerard.
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