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 A387454 #8 Aug 31 2025 10:26:29 %S A387454 9,8,8,8,3,0,8,2,6,2,2,5,1,2,8,5,4,5,0,6,9,7,4,2,8,8,2,9,3,4,0,0,8,6, %T A387454 1,3,0,6,5,2,5,1,0,1,3,5,7,4,1,8,7,7,0,6,3,9,9,4,9,6,9,2,7,1,6,0,2,1, %U A387454 3,5,3,3,0,9,8,7,2,6,0,9,9,2,4,9,3,4,3,1,8,9,9,6,8,1,7,4,1,9,3,0,8,6,8,8,8,7,1,7,9,1,2,9,1,6,1,0,5,1 %N A387454 Decimal expansion of cos(Pi/21). %H A387454 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 A387454 <a href="/index/Al#algebraic_06">Index entries for algebraic numbers, degree 6</a> %F A387454 Equals sin(19/42*Pi). %F A387454 Largest of the 6 real-valued roots of 64*x^6+32*x^5-96*x^4-48*x^3+32*x^2+16*x+1=0. %F A387454 4*this^3 -3*this = A073052. %F A387454 Equals 2F1(-1/14,1/14;1/2;3/4). - _R. J. Mathar_, Aug 31 2025 %e A387454 0.98883082622512854507... %Y A387454 Cf. A019688. %K A387454 nonn,cons,new %O A387454 0,1 %A A387454 _R. J. Mathar_, Aug 29 2025