OFFSET
1,2
COMMENTS
Also, decimal expansion of Sum_{h >= 0} 1/binomial(2*h,h). [From Renzo Sprugnoli]
LINKS
Michael Penn, So many factorials!!!, YouTube video, 2020.
Renzo Sprugnoli, Sums of Reciprocals of the Central Binomial Coefficients, INTEGERS, 6 (2006), #A27, page 9.
Eric Weisstein's World of Mathematics, Factorial Sums
FORMULA
Sum_{n>=0} (n!)^2/(2n)!.
Equals A073016 plus 1. - R. J. Mathar, Sep 08 2008
EXAMPLE
1.736399858718715077909795168364923496063125832909497905682196652308471818...
MATHEMATICA
RealDigits[N[(2 (18 + Pi Sqrt@3))/27, 120]] // First (* Michael De Vlieger, Sep 11 2015 *)
PROG
(PARI) default(realprecision, 2000); 2*(18 + sqrt(3)*Pi)/27 \\ Anders Hellström, Sep 11 2015
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Eric W. Weisstein, Jan 28 2004
STATUS
approved