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 A121598 #14 Aug 29 2025 12:57:09
%S A121598 2,3,0,4,7,6,4,8,7,0,9,6,2,4,8,6,5,0,5,2,4,1,1,5,0,2,2,3,5,4,6,8,5,5,
%T A121598 1,1,3,4,4,4,5,0,1,8,8,7,6,0,6,3,2,1,1,6,2,0,6,3,1,0,6,2,9,6,4,6,6,8,
%U A121598 5,3,3,4,2,7,7,8,4,7,9,5,9,6,3,7,9,1,1,1,4,2,1,9,7,4,7,6,1,7,9,3,6,1,5,1,5
%N A121598 Decimal expansion of cosecant of 180/7 = 25.7142857+ degrees = csc(Pi/7).
%C A121598 1 + csc(Pi/7) is the radius of the smallest circle into which 8 unit circles can be packed ("r=3.304+ Proved by Braaksma in 1963.", according to the Friedman link, which has a diagram).
%C A121598 csc(Pi/7) is the distance between the center of the larger circle and the center of each unit circle that touches the larger circle.
%H A121598 G. C. Greubel, <a href="/A121598/b121598.txt">Table of n, a(n) for n = 1..10000</a>
%H A121598 E. Friedman, <a href="https://erich-friedman.github.io/packing/cirincir/">Erich's Packing Center: "Circles in Circles"</a>
%H A121598 <a href="/index/Al#algebraic_06">Index entries for algebraic numbers, degree 6</a>.
%F A121598 Largest of the 6 real-values roots of 7*x^6 -56*x^4 +112*x^2 -64 =0. - _R. J. Mathar_, Aug 29 2025
%e A121598 2.304764870962486505241150223546855...
%t A121598 RealDigits[Csc[Pi/7], 10, 100][[1]] (* _G. C. Greubel_, Nov 02 2018 *)
%o A121598 (PARI) 1/sin(Pi/7)
%o A121598 (Magma) SetDefaultRealField(RealField(100)); R:= RealField(); 1/Sin(Pi(R)/7); // _G. C. Greubel_, Nov 02 2018
%Y A121598 Cf. A121570.
%K A121598 cons,nonn,changed
%O A121598 1,1
%A A121598 _Rick L. Shepherd_, Aug 09 2006