OFFSET
0,1
COMMENTS
Equals Sum_{n>=1} (-1)^(n+1)*binomial(2n,n)/(n*4^n). A factor 2 is missing in the Lehmer publication.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..10000
D. H. Lehmer, Interesting series involving the Central Binomial Coefficient, Am. Math. Monthly 92, no 7 (1985) 449-457.
FORMULA
0.3764528129191954316... = 2*0.1882264064595977158153772035... = 2*log(1.2071067811865...)
MAPLE
2*log(1/2+1/sqrt(2)) ;
MATHEMATICA
RealDigits[2Log[1/2+1/Sqrt[2]], 10, 120][[1]] (* Harvey P. Dale, Apr 12 2017 *)
PROG
(PARI) default(realprecision, 100); 2*log(1/2+1/sqrt(2)) \\ G. C. Greubel, Oct 02 2018
(Magma) SetDefaultRealField(RealField(100)); 2*Log(1/2+1/Sqrt(2)); // G. C. Greubel, Oct 02 2018
CROSSREFS
KEYWORD
AUTHOR
R. J. Mathar, Mar 04 2009
STATUS
approved