OFFSET
1,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
Anthony J. Guttmann, Spanning tree generating functions and Mahler measure, arXiv:1207.2815 [math-ph], 2012.
Sheldon Yang, Some properties of Catalan's constant G, Internat. J. Math. Ed. Sci. Tech. 23 (4) (1992) 549-556, L*(1).
FORMULA
From Amiram Eldar, Jul 22 2020: (Start)
Equals 1 + Sum_{k>=1} (2*k-1)!!^2/((2*k)!!^2 * (2*k + 1)).
Equals Sum_{k>=0} binomial(2*k,k)^2/(16^k * (2*k + 1)). (End)
EXAMPLE
1.1662436161232751205...
MAPLE
evalf(Catalan*4/Pi) ;
MATHEMATICA
RealDigits[4*Catalan/Pi, 10, 100][[1]] (* G. C. Greubel, Aug 23 2018 *)
PROG
(PARI) default(realprecision, 100); 4*Catalan/Pi \\ G. C. Greubel, Aug 23 2018
(Magma) R:= RealField(100); 4*Catalan(R)/Pi(R); // G. C. Greubel, Aug 23 2018
CROSSREFS
KEYWORD
AUTHOR
R. J. Mathar, Oct 27 2012
STATUS
approved