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 A019961 #17 Aug 31 2025 12:36:36 %S A019961 1,9,6,2,6,1,0,5,0,5,5,0,5,1,5,0,5,8,2,3,0,4,6,4,0,4,2,6,2,1,1,8,9,4, %T A019961 9,8,5,0,5,6,7,1,0,7,5,2,5,7,6,7,3,4,1,8,7,0,2,0,9,6,3,5,7,2,7,5,6,2, %U A019961 7,0,3,1,7,4,8,3,4,8,7,9,8,7,8,3,4,9,9,1,9,3,0,5,9,4,9,2,2,3,6 %N A019961 Decimal expansion of tangent of 63 degrees. %C A019961 Also the decimal expansion of cotangent of 27 degrees. - _Ivan Panchenko_, Sep 01 2014 %H A019961 Ivan Panchenko, <a href="/A019961/b019961.txt">Table of n, a(n) for n = 1..1000</a> %H A019961 Wikipedia, <a href="http://en.wikipedia.org/wiki/Exact_trigonometric_constants">Exact trigonometric constants</a> %H A019961 <a href="/index/Al#algebraic_08">Index entries for algebraic numbers, degree 8</a> %F A019961 Equals cot(3*Pi/20) = sqrt(5) - 1 + sqrt(5 - 2*sqrt(5)). - _G. C. Greubel_, Nov 21 2018 %F A019961 Root of x^8-44*x^6+166*x^4-44*x^2+1=0. - _R. J. Mathar_, Aug 31 2025 %e A019961 1.96261050550515058230464042621189498505671... %t A019961 RealDigits[Tan[7*Pi/20], 10, 100][[1]] (* _G. C. Greubel_, Nov 21 2018 *) %o A019961 (PARI) default(realprecision, 100); tan(7*Pi/20) \\ _G. C. Greubel_, Nov 21 2018 %o A019961 (Magma) SetDefaultRealField(RealField(100)); R:= RealField(); Tan(7*Pi(R)/20); // _G. C. Greubel_, Nov 21 2018 %o A019961 (Sage) numerical_approx(tan(7*pi/20), digits=100) # _G. C. Greubel_, Nov 21 2018 %Y A019961 Cf. A019872 (sine of 63 degrees). %K A019961 nonn,cons,changed %O A019961 1,2 %A A019961 _N. J. A. Sloane_