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A012183 sec(tan(arctanh(x)))=1+1/2!*x^2+21/4!*x^4+1101/6!*x^6+107209/8!*x^8... 0
1, 1, 21, 1101, 107209, 16711481, 3810146205, 1195529025861, 494050576455185, 260086639760540401, 169928807728242392485, 134924876918419856397501, 127963083862513681084495321 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..12.

CROSSREFS

Sequence in context: A220637 A143003 A193156 * A012230 A270505 A086098

Adjacent sequences:  A012180 A012181 A012182 * A012184 A012185 A012186

KEYWORD

nonn

AUTHOR

Patrick Demichel (patrick.demichel(AT)hp.com)

STATUS

approved

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Last modified February 17 15:19 EST 2019. Contains 320220 sequences. (Running on oeis4.)