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 A263809 #7 Oct 27 2015 07:33:52
%S A263809 2,7,8,6,4,0,7,8,5,9,3,7,1,3,5,3,7,1,8,3,6,8,4,9,2,5,2,0,6,5,0,7,3,6,
%T A263809 4,8,5,3,1,4,9,6,2,4,3,5,0,3,1,2,3,5,7,5,7,9,4,8,5,6,3,2,6,3,7,6,0,6,
%U A263809 4,8,0,2,5,1,5,0,0,7,3,2,6,1,3,5,7,2,9,4,6,5,9,7,1,5,6,1,9,1,1,1,9,9,3,1,3
%N A263809 Decimal expansion of C_{1/2}, a constant related to Kolmogorov's inequalities.
%D A263809 Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 7.7 Riesz-Kolmogorov Constants, p. 474.
%H A263809 Burgess Davis, <a href="http://dx.doi.org/10.2307/1997664">On Kolmogorov's Inequalities</a>, Transactions of the American Mathematical Society Vol. 222 (Sep., 1976), pp. 179-192.
%F A263809 C_{1/2} = gamma(1/4)^2/(Pi*gamma(3/4)^2).
%F A263809 Equals (1/Pi^2)*(integral_{0..Pi} sqrt(csc(t)) dt)^2.
%F A263809 Also equals (8/Pi^2)*A093341^2.
%e A263809 2.78640785937135371836849252065073648531496243503123575794856326376...
%t A263809 RealDigits[Gamma[1/4]^2/(Pi*Gamma[3/4]^2), 10, 105] // First
%o A263809 (PARI) gamma(1/4)^2/(Pi*gamma(3/4)^2) \\ _Michel Marcus_, Oct 27 2015
%Y A263809 Cf. A068465, A068466, A093341, A242822.
%K A263809 nonn,cons,easy
%O A263809 1,1
%A A263809 _Jean-François Alcover_, Oct 27 2015