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 A346781 a(n) is the numerator of the sum of the first n terms of 1 - 1/3 - 1/5 + 1/7 + 1/9 - 1/11 - 1/13 + ... . 1
 1, 2, 7, 64, 227, 2182, 24901, 27904, 519413, 9103082, 8410247, 207985216, 1106853941, 3134651098, 85885292267, 2808012157952, 2944757946677, 402260886146, 14238994069127, 14850593365952, 632726700580207, 26229300849325726, 25294817897063581, 1230908174013784832 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The limit for n->oo of the sum 1 - 1/3 - 1/5 + 1/7 + ... is log(1+sqrt(2))/sqrt(2) (A196525). See there for more information. REFERENCES Barry Mazur, Chapter IV.1 Algebraic Numbers, page 316, in The Princeton Companion to Mathematics, ed. Timothy Gowers, Princeton University Press, Princeton and Oxford, 2008. LINKS Table of n, a(n) for n=1..24. EXAMPLE 1, 2/3, 7/15, 64/105, 227/315, 2182/3465, 24901/45045, 27904/45045, ... PROG (PARI) a346781(limit)={my(s=0, b(n)=1/(n*sign(4-(n+2)%8))); forstep(k=1, limit, 2, print1(numerator(s+=b(k)), ", "))}; a346781(47) CROSSREFS The corresponding denominators are A025547. Cf. A091337, A196525. Sequence in context: A100523 A181030 A006506 * A011821 A366705 A117263 Adjacent sequences: A346778 A346779 A346780 * A346782 A346783 A346784 KEYWORD nonn,frac AUTHOR Hugo Pfoertner, Aug 03 2021 STATUS approved

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Last modified July 25 00:10 EDT 2024. Contains 374585 sequences. (Running on oeis4.)