OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..10000
D. H. Lehmer, Euler constants for arithmetic progressions, Acta Arith. 27 (1975), p. 134.
FORMULA
Equals EulerGamma/5 + Pi/10*sqrt(1 - 2/sqrt(5)) + log(5)/20 - sqrt(5)/10*log((1 + sqrt(5))/2).
Equals Sum_{n>=0} (1/(5n+2) - 2/5*arctanh(5/(10n+9))).
EXAMPLE
0.190389326430203154225983229764268163260151948448458487...
MATHEMATICA
RealDigits[-Log[5]/5 - PolyGamma[2/5]/5, 10, 105] // First
PROG
(PARI) Euler/5 + Pi/10*sqrt(1 - 2/sqrt(5)) + log(5)/20 - sqrt(5)/10*log((1 + sqrt(5))/2) \\ Michel Marcus, Apr 10 2015
(Magma) SetDefaultRealField(RealField(100)); R:= RealField(); EulerGamma(R)/5 + Pi(R)/10*Sqrt(1 - 2/Sqrt(5)) + Log(5)/20 - Sqrt(5)/10*Log((1 + Sqrt(5))/2); // G. C. Greubel, Aug 28 2018
CROSSREFS
KEYWORD
AUTHOR
Jean-François Alcover, Apr 10 2015
STATUS
approved