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 A133731 #41 May 07 2025 18:56:32
%S A133731 1,1,5,8,7,2,8,4,7,3,0,1,8,1,2,1,5,1,7,8,2,8,2,3,3,5,0,9,9,3,3,5,0,9,
%T A133731 1,4,9,6,8,8,2,9,2,2,6,6,4,9,2,0,9,6,5,1,1,8,2,0,6,9,5,8,8,4,8,2,0,6,
%U A133731 6,9,8,0,2,5,5,9,1,9,6,0,9,3,1,9,9,3,2,1,6,1,0,7,3,0,8,6,0,4,3,8,1,7,5,9,6
%N A133731 Decimal expansion of goat tether length to graze half a unit field.
%C A133731 See Ullisch link for a closed form. - _Charles R Greathouse IV_, Jul 08 2023
%D A133731 Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 8.2, p. 487.
%D A133731 Ingo Ullisch, A Closed-Form Solution to the Geometric Goat Problem, The Mathematical Intelligencer volume 42 (2020), pp. 12-16.
%H A133731 Michael Johannes Latsky, <a href="/A133731/b133731.txt">Table of n, a(n) for n = 1..20000</a>
%H A133731 M. Fraser, <a href="http://www.jstor.org/stable/2690163">A tale of two goats</a>, Math. Mag., 55 (1982), 221-227. Has extensive bibliography.
%H A133731 James Grime and Brady Haran, <a href="https://www.youtube.com/watch?v=ZdQFN2XKeKI">The Goat Problem</a>, Numberphile video (2023).
%H A133731 Graham Jameson and Nicholas Jameson, <a href="http://nojameson.net/goat.pdf">Goats and birds</a>, The Mathematical Gazette, Volume 101, Issue 551 (July 2017), pp. 296-300.
%H A133731 Gerd Lamprecht, <a href="http://www.gerdlamprecht.de/langeZahlen/1158728473.pdf">A133731=cos(A173201/2)*2; 10000 digits</a> [Gerd Lamprecht (gerdlamprecht(AT)googlemail.com), Feb 12 2010]
%H A133731 Gerd Lamprecht, <a href="http://www.gerdlamprecht.de/Roemisch_JAVA.htm#ZZZZZ0004">Iterationsrechner mit Algorithmus</a> [Gerd Lamprecht (gerdlamprecht(AT)googlemail.com), Feb 12 2010]
%H A133731 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GoatProblem.html">Goat Problem</a>.
%F A133731 Equals cos(A173201/2)*2. - Gerd Lamprecht (gerdlamprecht(AT)googlemail.com), Feb 12 2010
%e A133731 1.1587284730181215178...
%t A133731 A173201 = x /. FindRoot[(-x*Cos[x] + Sin[x] - Pi/2)/(Sin[x]*x), {x, 1}, WorkingPrecision -> 105]; RealDigits[2*Cos[A173201/2] ][[1]] (* _Jean-François Alcover_, Oct 31 2012 *)
%o A133731 (PARI) cos(solve(x=1,2,sin(x)-x*cos(x)-Pi/2)/2)*2 \\ _Charles R Greathouse IV_, Mar 03 2021
%K A133731 nonn,cons
%O A133731 1,3
%A A133731 _Eric W. Weisstein_, Sep 21 2007