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 A387447 #11 Aug 31 2025 10:22:13 %S A387447 9,9,3,2,3,8,3,5,7,7,4,1,9,4,2,9,8,8,5,4,7,8,9,5,5,5,2,1,9,3,7,0,4,3, %T A387447 4,0,3,4,9,1,0,6,1,9,7,0,7,0,6,9,3,7,0,2,5,6,5,0,0,7,1,8,8,0,1,6,2,7, %U A387447 8,6,0,5,1,5,0,5,1,2,6,3,3,6,8,0,1,7,2,0,7,1,5,3,9,2,5,9,1,2,2,5,4,3,6,1,2,1,7,2,7,0,3,5,7,6,6,3,1,6 %N A387447 Decimal expansion of cos(Pi/27). %H A387447 R. J. Mathar, <a href="https://vixra.org/abs/2210.0026">Reduction formulas of the cosine of integer fractions of pi</a>, (2008) vixra:2210.0026 %H A387447 <a href="/index/Al#algebraic_09">Index entries for algebraic numbers, degree 9</a> %F A387447 Equals sin(25*Pi/54) = 2F1(-1/18,1/18;1/2;3/4). %F A387447 Largest of the 9 real-valued roots of 512*x^9 -1152*x^7 +864*x^5 -240*x^3 +18*x -1 =0. %F A387447 4*this^3 -3*this = A019879. %e A387447 0.99323835774194298855... %K A387447 nonn,cons,new %O A387447 0,1 %A A387447 _R. J. Mathar_, Aug 29 2025