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A101922 Numerators of expansion of 2^(-1/2) * arcsinh(cos(x)). 3
-1, -1, 11, 491, 11159, -460681, -103577629, -8160790429, 624333860399, 386787409545839, 68810049201689531, -6999828208693648549, -9872674440874152431161, -3255253386897615662908441 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

With sign pattern +--+--: numerators of expansion of 2^(-1/2) * asinh(cosh(x)).

Odd coefficients are zero, denominators are 2^n.

LINKS

Table of n, a(n) for n=1..14.

FORMULA

asinh(cos(x)) = log(sqrt(2)+1) + 1/sqrt(2) * [ -1/2*x^2/2! - 1/4*x^4/4! + 11/8*x^6/6! + 491/16*x^8/8! +...].

acosh(cos(x)) = Pi/2 - log(sqrt(2)+1) + 1/sqrt(2) * [1/2*x^2/2! + 1/4*x^4/4! - 11/8*x^6/6! - 491/16*x^8/8! -...].

CROSSREFS

Cf. A101924, A012495.

Sequence in context: A156863 A145516 A041931 * A263246 A263377 A142809

Adjacent sequences:  A101919 A101920 A101921 * A101923 A101924 A101925

KEYWORD

sign

AUTHOR

Ralf Stephan, Dec 27 2004

STATUS

approved

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Last modified February 24 11:06 EST 2018. Contains 299603 sequences. (Running on oeis4.)