A388745 - OEIS

%I #10 May 19 2026 22:24:58

%S 1,0,8,6,4,3,1,0,2,2,4,5,6,3,8,6,2,5,6,8,9,5,9,9,1,7,7,2,0,8,0,5,4,2,

%T 2,4,8,0,0,5,3,1,5,3,6,0,2,4,0,2,0,3,1,8,6,9,8,0,0,0,5,6,1,0,6,8,4,6,

%U 5,2,3,5,5,1,4,3,2,8,4,0,6,8,6,9,9,9,7

%N Decimal expansion of 2 * sqrt(2 * (2+sqrt(2))) * exp(-Pi/2).

%H Simon Plouffe, <a href="https://plouffe.fr/articles/numbers%20in%20the%20base_exp_english%202025.pdf">Numbers in the base e^Pi</a>, 2025.

%H <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>.

%F Empirical: Equals Sum_{k>=0} A208589(k) / exp(k*Pi).

%e 1.0864310224563862568959917720805422480...

%t First[RealDigits[2*Sqrt[2*(2 + Sqrt[2])]*Exp[-1/2*Pi], 10, 100]]

%o (PARI) 2 * exp(-Pi / 2) * sqrt(2) * (2+2^(1/2))^(1/2)

%Y Cf. A208589.

%K nonn,cons

%O 1,3

%A _Simon Plouffe_, Sep 18 2025