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A101924 Numerators of expansion of 2^(-1/2) * arccsch(cos(x)), even powers only. 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

arccsch(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! + ...).

arcsech(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: A274787 A116875 A303109 * 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 October 15 13:01 EDT 2018. Contains 316236 sequences. (Running on oeis4.)