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 A116425 #55 Feb 16 2025 08:33:00 %S A116425 3,2,4,6,9,7,9,6,0,3,7,1,7,4,6,7,0,6,1,0,5,0,0,0,9,7,6,8,0,0,8,4,7,9, %T A116425 6,2,1,2,6,4,5,4,9,4,6,1,7,9,2,8,0,4,2,1,0,7,3,1,0,9,8,8,7,8,1,9,3,7, %U A116425 0,7,3,0,4,9,1,2,9,7,4,5,6,9,1,5,1,8,8,5,0,1,4,6,5,3,1,7,0,7,4,3,3,3,4,1,1 %N A116425 Decimal expansion of 2 + 2*cos(2*Pi/7). %C A116425 A root of the equation x^3 - 5*x^2 + 6*x - 1 = 0. - _Arkadiusz Wesolowski_, Jan 13 2016 %C A116425 The other two roots of this minimal polynomial of the present algebraic number (rho(7))^2, with rho(7) = 2*cos(Pi/7) = A160389 are (2*cos(3*Pi/7))^2 = (A255241)^2 and (2*cos(5*Pi/7))^2 = (-A255249)^2. - _Wolfdieter Lang_, Mar 30 2020 %D A116425 Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.25 Tutte-Beraha Constants, p. 417. %H A116425 Jesús Salas and Alan D. Sokal, <a href="https://arxiv.org/abs/cond-mat/0004330">Transfer matrices and partition functions zeros for antiferromagnetic Potts models</a>, arXiv:cond-mat/0004330 [cond-mat.stat-mech], 2000-2001, p. 64. %H A116425 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LogisticMap.html">Logistic Map</a> %H A116425 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SilverConstant.html">Silver Constant</a> %H A116425 <a href="/index/Al#algebraic_03">Index entries for algebraic numbers, degree 3</a> %F A116425 Equals (2*cos(Pi/7))^2 = (A160389)^2. %F A116425 Equals 2 + i^(4/7) - i^(10/7). - _Peter Luschny_, Apr 04 2020 %F A116425 Let c = 2 + 2*cos(2*Pi/7). The linear fractional transformation z -> c - c/z has order 7, that is, z = c - c/(c - c/(c - c/(c - c/(c - c/(c - c/(c - c/z)))))). - _Peter Bala_, May 09 2024 %e A116425 3.246979603717467061... %t A116425 First@ RealDigits[N[2 + 2 Cos[2 Pi/7], 120]] (* _Michael De Vlieger_, Jan 13 2016 *) %o A116425 (PARI) 2 + 2*cos(2*Pi/7) \\ _Michel Marcus_, Jan 13 2016 %Y A116425 Cf. A231187, A160389. %Y A116425 Cf. A003558, A054142, A255241, A255249. %Y A116425 2 + 2*cos(2*Pi/n): A104457 (n = 5), A332438 (n = 9), A296184 (n = 10), A019973 (n = 12). %K A116425 nonn,cons,easy %O A116425 1,1 %A A116425 _Eric W. Weisstein_, Feb 15 2006