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 A334071 Decimal expansion of Sum_{k >= 1} 2^(-phi(k)), where phi is the Euler totient function (A000010). 2
 2, 0, 8, 5, 5, 6, 1, 8, 8, 2, 5, 9, 7, 4, 1, 4, 6, 5, 2, 6, 3, 0, 3, 8, 7, 0, 8, 3, 2, 8, 4, 7, 4, 7, 5, 6, 1, 6, 1, 2, 1, 0, 7, 7, 6, 0, 3, 2, 3, 8, 7, 3, 7, 1, 9, 4, 7, 5, 7, 9, 3, 8, 8, 3, 1, 3, 6, 1, 8, 0, 1, 3, 3, 7, 1, 0, 5, 8, 8, 2, 1, 7, 1, 0, 3, 1, 9 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This constant is irrational (Erdős and Graham, 1980). LINKS Table of n, a(n) for n=1..87. Paul Erdős and Ronald L. Graham, Old and new problems and results in combinatorial number theory, L'enseignement Mathématique, Université de Genève, 1980. EXAMPLE 2.08556188259741465263038708328474756161210776032387... MATHEMATICA RealDigits[Sum[2^(-EulerPhi[n]), {n, 1, 2000}], 10, 100][[1]] PROG (PARI) suminf(k=1, 1/2^eulerphi(k)) \\ Michel Marcus, Apr 14 2020 CROSSREFS Cf. A000010, A334072. Sequence in context: A185348 A321599 A020780 * A243406 A293934 A356651 Adjacent sequences: A334068 A334069 A334070 * A334072 A334073 A334074 KEYWORD nonn,cons AUTHOR Amiram Eldar, Apr 13 2020 STATUS approved

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Last modified September 28 14:24 EDT 2023. Contains 365735 sequences. (Running on oeis4.)