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A012821 exp(sec(x)*arcsinh(x))=1+x+1/2!*x^2+3/3!*x^3+9/4!*x^4+45/5!*x^5... 0
1, 1, 1, 3, 9, 45, 225, 1071, 6993, 56697, 467745, 3279419, 29529753, 376156261, 4297350785, 35274762407, 378759492257, 8003761282417, 122599030798017, 853554115621363, 8002975063348265, 450081179390735645 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

The first negative number is a(24)= -686072407102337430543.

LINKS

Table of n, a(n) for n=0..21.

CROSSREFS

Sequence in context: A192891 A068100 A262129 * A229813 A262130 A262131

Adjacent sequences:  A012818 A012819 A012820 * A012822 A012823 A012824

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified November 21 16:08 EST 2017. Contains 295003 sequences.