OFFSET
0,1
LINKS
MathOverflow, How to calculate the infinite sum of this double series?, 2014.
Eric Weisstein's World of Mathematics, Jacobi Theta Functions.
FORMULA
Also equals theta_2(0,exp(-Pi)), where 'theta' is the elliptic theta function.
Equals Product_{k>=1} tanh(k*Pi/2). - Amiram Eldar, Jun 12 2021
EXAMPLE
0.913579138156116821407242593401222089701963916393469...
MATHEMATICA
RealDigits[(Pi/2)^(1/4)/Gamma[3/4], 10, 103] // First
PROG
(PARI) (Pi/2)^(1/4)/gamma(3/4) \\ Michel Marcus, Dec 15 2014
CROSSREFS
KEYWORD
AUTHOR
Jean-François Alcover, Dec 15 2014
STATUS
approved