OFFSET
1,3
COMMENTS
This constant is transcendental.
FORMULA
Equals Sum_{k>=1} Pi^(2*k-1)/(4^k*(2*k-1)!).
Equals Product_{k>=2} (1 + (-1)^k/k^2).
Equals (i^(-i) - i^i)/4, where i is the imaginary unit.
EXAMPLE
(1 + 1/2^2) * (1 - 1/3^2) * (1 + 1/4^2) * (1 - 1/5^2) * (1 + 1/6^2) * ... = (e^(Pi/2) - e^(-Pi/2))/4 = 1.15064945115364743673152001...
MATHEMATICA
RealDigits[Sinh[Pi/2]/2, 10, 110] [[1]]
PROG
(PARI) sinh(Pi/2)/2 \\ Michel Marcus, Apr 28 2020
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Ilya Gutkovskiy, Apr 28 2020
STATUS
approved