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A101924 Numerators of expansion of 2^(-1/2) * arccsch(cos(x)). 1
1, 7, 109, 3163, 166201, 14952367, 2002052389, 353291166403, 77829008955121, 21170264082173527, 7106489649576530269, 2913186117837522604843, 1426879448953133350342441, 816516326741659045770111487 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Odd coefficients are zero, denominators are 2^n.

LINKS

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

FORMULA

acsch(cos(x)) = log(sqrt(2)+1) + 1/sqrt(2) * [ -1/2*x^2/2! + 7/4*x^4/4! + 109/8*x^6/6! + 3163/16*x^8/8! +...].

asech(cos(x)) = Pi/2 - log(sqrt(2)+1) - 1/sqrt(2) * [ -1/2*x^2/2! + 7/4*x^4/4! + 109/8*x^6/6! + 3163/16*x^8/8! +...].

CROSSREFS

Cf. A101922, A012495.

Sequence in context: A239848 A274787 A116875 * A171193 A212371 A112463

Adjacent sequences:  A101921 A101922 A101923 * A101925 A101926 A101927

KEYWORD

nonn

AUTHOR

Ralf Stephan, Dec 27 2004

STATUS

approved

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Last modified February 25 00:39 EST 2018. Contains 299630 sequences. (Running on oeis4.)