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 A019938 #19 Aug 31 2025 12:52:40 %S A019938 8,3,9,0,9,9,6,3,1,1,7,7,2,8,0,0,1,1,7,6,3,1,2,7,2,9,8,1,2,3,1,8,1,3, %T A019938 6,4,6,8,7,4,3,4,2,8,3,0,1,2,3,4,6,5,3,3,2,4,4,1,0,2,0,3,9,2,3,2,5,1, %U A019938 8,3,2,8,0,5,5,0,3,4,5,2,1,7,6,0,8,0,6,7,2,4,1,1,3,1,2,8,8,3,0 %N A019938 Decimal expansion of tangent of 40 degrees. %C A019938 Also the decimal expansion of cotangent of 50 degrees. - _Ivan Panchenko_, Aug 01 2014 %H A019938 Ivan Panchenko, <a href="/A019938/b019938.txt">Table of n, a(n) for n = 0..1000</a> %H A019938 <a href="/index/Al#algebraic_06">Index entries for algebraic numbers, degree 6</a>. %F A019938 One of the 6 real-valued roots of x^6-33*x^4+27*x^2-3=0. - _R. J. Mathar_, Aug 31 2025 %F A019938 Equals A019849/A019859. - _R. J. Mathar_, Aug 31 2025 %e A019938 0.839099631177280011763127298123181364687434283012346533244102... %t A019938 RealDigits[Tan[2*Pi/9], 10, 100][[1]] (* _G. C. Greubel_, Nov 25 2018 *) %t A019938 RealDigits[Tan[40 Degree],10,120][[1]] (* _Harvey P. Dale_, Apr 06 2022 *) %o A019938 (PARI) default(realprecision, 100); tan(2*Pi/9) \\ _G. C. Greubel_, Nov 25 2018 %o A019938 (PARI) polrootsreal(x^6-33*x^4+27*x^2-3)[5] \\ _Charles R Greathouse IV_, Feb 05 2025 %o A019938 (Magma) SetDefaultRealField(RealField(100)); R:= RealField(); Tan(2*Pi(R)/9); // _G. C. Greubel_, Nov 25 2018 %o A019938 (Sage) numerical_approx(tan(2*pi/9), digits=100) # _G. C. Greubel_, Nov 25 2018 %Y A019938 Cf. A019849 (sine of 40 degrees). %K A019938 nonn,cons,changed %O A019938 0,1 %A A019938 _N. J. A. Sloane_