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 A102771 #26 Feb 16 2025 08:32:56 %S A102771 1,7,2,0,4,7,7,4,0,0,5,8,8,9,6,6,9,2,2,7,5,9,0,1,1,9,7,7,3,8,8,6,0,9, %T A102771 5,9,9,4,0,7,3,7,4,1,7,0,0,1,0,1,9,8,3,2,9,2,0,7,0,9,4,7,0,7,0,2,3,8, %U A102771 6,8,9,9,2,2,0,8,9,6,6,2,3,1,3,3,2,4,4,1,2,4,1,3,8,7,5,8,7,7,4 %N A102771 Decimal expansion of area of a regular pentagon with unit edge length. %H A102771 G. C. Greubel, <a href="/A102771/b102771.txt">Table of n, a(n) for n = 1..10000</a> %H A102771 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Pentagon.html">Pentagon</a> %H A102771 <a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a> %F A102771 Equals sqrt(25 + 10*sqrt(5)) / 4. %F A102771 Equals (3*phi+1)*sqrt(3-phi) with the golden section phi = (1 + sqrt(5))/2. - _Wolfdieter Lang_, Jan 25 2013 %F A102771 Equals 5/(4*tan(Pi/5)). - _Michel Marcus_, Mar 25 2015 %F A102771 Equals (5/4)*sqrt(phi^3/sqrt(5)). - _G. C. Greubel_, Jul 03 2017 %e A102771 1.720477400588966922759011977... %t A102771 RealDigits[(5/4)*Sqrt[GoldenRatio^3/Sqrt[5]], 10, 50][[1]] (* _G. C. Greubel_, Jul 03 2017 *) %o A102771 (PARI) 5/(4*tan(Pi/5)) \\ _Michel Marcus_, Mar 25 2015 %Y A102771 Cf. Areas of other regular polygons: A120011, A104956, A178817, A090488, A256853, A178816, A256854, A178809. %K A102771 nonn,cons %O A102771 1,2 %A A102771 Bryan Jacobs (bryanjj(AT)gmail.com), Feb 10 2005 %E A102771 Corrected the title. - _Stanislav Sykora_, Apr 12 2015