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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 A316133

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 16 23:53 EDT 2021. Contains 347477 sequences. (Running on oeis4.)