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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 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 January 19 21:52 EST 2019. Contains 319310 sequences. (Running on oeis4.)