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 A019851 #34 Aug 31 2025 11:43:50 %S A019851 6,6,9,1,3,0,6,0,6,3,5,8,8,5,8,2,1,3,8,2,6,2,7,3,3,3,0,6,8,6,7,8,0,4, %T A019851 7,3,5,9,9,5,8,3,2,1,8,9,5,9,7,9,5,6,7,6,8,1,7,4,5,3,3,5,2,2,8,7,9,6, %U A019851 6,6,0,1,7,1,0,6,4,3,8,9,7,1,4,6,1,5,4,9,2,3,3,6,0,0,9,0,0,6,7 %N A019851 Decimal expansion of sine of 42 degrees. %C A019851 This sequence is also decimal expansion of cosine of 48 degrees. - _Mohammad K. Azarian_, Jun 29 2013 %C A019851 A quartic number with denominator 2. - _Charles R Greathouse IV_, Nov 05 2017 %H A019851 Ivan Panchenko, <a href="/A019851/b019851.txt">Table of n, a(n) for n = 0..1000</a> %H A019851 Wikipedia, <a href="http://en.wikipedia.org/wiki/Exact_trigonometric_constants">Exact trigonometric constants</a> %H A019851 <a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a> %F A019851 Equals cos(4*Pi/15) = (sqrt(5)-1)*(sqrt(3)*sqrt(5+2*sqrt(5))-1)/8 = 8*A019887^4 -8*A019887^2 + 1 = sqrt(1-A019857^2). - _R. J. Mathar_, Jun 18 2006 %F A019851 Equals 2*A019830*A019878. - _R. J. Mathar_, Jan 17 2021 %F A019851 A root of 16*x^4-8*x^3-16*x^2+8*x+1 =0. - _R. J. Mathar_, Aug 31 2025 %e A019851 0.6691306... %o A019851 (PARI) sin(7/30*Pi) \\ _Charles R Greathouse IV_, Nov 05 2017 %Y A019851 Cf. A019857, A019887, A019830, A019878. %K A019851 nonn,cons,changed %O A019851 0,1 %A A019851 _N. J. A. Sloane_