This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A248557 #36 Feb 16 2025 08:33:23
%S A248557 9,1,3,5,7,9,1,3,8,1,5,6,1,1,6,8,2,1,4,0,7,2,4,2,5,9,3,4,0,1,2,2,2,0,
%T A248557 8,9,7,0,1,9,6,3,9,1,6,3,9,3,4,6,9,0,3,3,4,1,9,6,9,6,5,3,1,2,6,5,9,0,
%U A248557 8,0,0,9,3,7,2,0,0,9,1,1,3,9,6,3,2,8,8,9,8,3,3,5,9,5,8,0,1,3,8,8,9,8,5
%N A248557 Decimal expansion of (Pi/2)^(1/4)/Gamma(3/4).
%H A248557 MathOverflow, <a href="http://mathoverflow.net/questions/189199">How to calculate the infinite sum of this double series?</a>, 2014.
%H A248557 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/JacobiThetaFunctions.html">Jacobi Theta Functions</a>.
%F A248557 Also equals theta_2(0,exp(-Pi)), where 'theta' is the elliptic theta function.
%F A248557 Equals A175573 / exp(4*A251992/Pi + Pi/4).
%F A248557 Equals Product_{k>=1} tanh(k*Pi/2). - _Amiram Eldar_, Jun 12 2021
%e A248557 0.913579138156116821407242593401222089701963916393469...
%t A248557 RealDigits[(Pi/2)^(1/4)/Gamma[3/4], 10, 103] // First
%o A248557 (PARI) (Pi/2)^(1/4)/gamma(3/4) \\ _Michel Marcus_, Dec 15 2014
%Y A248557 Cf. A010767, A068465, A092040, A175573, A222068, A251992.
%K A248557 nonn,cons,easy
%O A248557 0,1
%A A248557 _Jean-François Alcover_, Dec 15 2014