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 A254615 #25 Jul 01 2023 14:03:00
%S A254615 1,0,8,8,4,6,4,5,5,4,0,4,4,3,9,7,3,9,2,0,2,6,6,0,5,3,9,9,5,4,4,9,0,1,
%T A254615 7,7,9,4,0,7,2,2,4,0,5,8,7,6,5,9,5,8,3,1,2,4,3,9,4,3,1,7,3,5,2,1,8,8,
%U A254615 2,6,0,5,8,4,9,2,2,2,9,4,6,9,1,3,0,4,8,4,3,8,1,8,2,7,3,2,4,0,0,1
%N A254615 Decimal expansion of the left Alzer's constant x.
%C A254615 The left Alzer's constant x is defined to be the best constant in the left Alzer's inequality: x*abs(sin(cos a) + sin(sin a)) <= abs(cos a + sin a), where a is any real number.
%H A254615 Horst Alzer, <a href="https://doi.org/10.4171/EM/139">A trigonometric double-inequality</a>, Elemente der Mathematik 65 (2010), 45-48.
%F A254615 x = (sqrt(2)*sin(1/sqrt(2)))^(-1).
%F A254615 x = Sum_{k=-oo..oo} (-1)^k/(1 - 2*(Pi*k)^2). - _Bruno Berselli_, Feb 03 2015
%e A254615 x = 1.088464554044397392026605399544901779407224058765958312439431735...
%t A254615 RealDigits[(Sqrt[2] Sin[1/Sqrt[2]])^(-1), 10, 100][[1]] (* _Bruno Berselli_, Feb 03 2015 *)
%o A254615 (PARI) 1/(sqrt(2)*sin(1/sqrt(2))) \\ _Michel Marcus_, Feb 03 2015
%K A254615 nonn,cons
%O A254615 1,3
%A A254615 _Roman Witula_, Feb 03 2015