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 A087197 #30 Feb 16 2025 08:32:51
%S A087197 5,6,4,1,8,9,5,8,3,5,4,7,7,5,6,2,8,6,9,4,8,0,7,9,4,5,1,5,6,0,7,7,2,5,
%T A087197 8,5,8,4,4,0,5,0,6,2,9,3,2,8,9,9,8,8,5,6,8,4,4,0,8,5,7,2,1,7,1,0,6,4,
%U A087197 2,4,6,8,4,4,1,4,9,3,4,1,4,4,8,6,7,4,3,6,6,0,2,0,2,1,0,7,3,6,3,4,4,3,0,2,8
%N A087197 Decimal expansion of 1/sqrt(Pi).
%C A087197 Radius of a circle with area 1.
%C A087197 Expectation of the maximum of a size 2 sample from a normal (0,1) distribution. - _Jean-François Alcover_, Jun 05 2014
%D A087197 Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.16 Extreme value constants, p. 365.
%H A087197 G. C. Greubel, <a href="/A087197/b087197.txt">Table of n, a(n) for n = 0..5000</a>
%H A087197 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/InverseErf.html">Inverse Erf</a>
%H A087197 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F A087197 Equals lim_{n -> infinity} Catalan(n)/(4^n*n^(-3/2)). - _Jean-François Alcover_, May 23 2013
%F A087197 Equals Sum_{k>=1} k/(2^k * Gamma(k+3/2)). - _Amiram Eldar_, May 27 2021
%e A087197 0.56418958354775628694...
%t A087197 RealDigits[1/Sqrt[Pi], 10, 50][[1]] (* _G. C. Greubel_, Jan 09 2017 *)
%o A087197 (PARI) Pi^-.5 \\ _Charles R Greathouse IV_, Nov 13 2015
%Y A087197 Cf. A086201, A087198, A087199.
%K A087197 cons,easy,nonn
%O A087197 0,1
%A A087197 _Sven Simon_, Aug 24 2003