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A256936 Decimal expansion of Sum_{n>=1} phi(n)/2^n, where phi is Euler's totient function. 0
1, 3, 6, 7, 6, 3, 0, 8, 0, 1, 9, 8, 5, 0, 2, 2, 3, 5, 0, 7, 9, 0, 5, 0, 8, 1, 4, 6, 2, 1, 3, 0, 8, 8, 1, 3, 9, 0, 7, 4, 8, 9, 1, 9, 9, 8, 9, 6, 2, 7, 9, 4, 8, 5, 2, 9, 5, 6, 5, 9, 8, 4, 6, 3, 7, 6, 2, 1, 5, 6, 7, 1, 0, 3, 9, 7, 6, 6, 8, 7, 4, 4, 5, 5, 0, 3, 7, 9, 0, 0, 7, 0, 5, 4, 2, 8, 2, 8, 0 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Richard K. Guy, Unsolved Problems in Number Theory, Springer (2004) p. 139.

LINKS

Table of n, a(n) for n=1..99.

Eric Weisstein's MathWorld, Totient Function

Wikipedia, Euler's totient function

EXAMPLE

1.36763080198502235079050814621308813907489199896...

MATHEMATICA

digits = 99; m0 = 10; dd = 10; Clear[f]; f[m_] := f[m] = Sum[EulerPhi[n]/2^n, {n, 1, m}] // N[#, digits + 2*dd]&; f[m = m0] ; While[RealDigits[f[2*m], 10, digits + dd ] != RealDigits[f[m], 10, digits + dd ], m = 2*m; Print[m]]; RealDigits[f[m], 10, digits] // First

PROG

(PARI) suminf(n=1, eulerphi(n)/2^n) \\ Charles R Greathouse IV, Apr 20 2016

CROSSREFS

Cf. A000010.

Sequence in context: A156648 A278688 A016616 * A021276 A290943 A067753

Adjacent sequences:  A256933 A256934 A256935 * A256937 A256938 A256939

KEYWORD

nonn,cons

AUTHOR

Jean-Fran├žois Alcover, Apr 13 2015

STATUS

approved

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Last modified October 22 21:09 EDT 2018. Contains 316504 sequences. (Running on oeis4.)