cp's OEIS Frontend

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.

A187426 Decimal expansion of (3-phi)^2 = 10 - 5*phi where phi is the golden ratio.

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%I A187426 #46 Feb 04 2025 14:55:38
%S A187426 1,9,0,9,8,3,0,0,5,6,2,5,0,5,2,5,7,5,8,9,7,7,0,6,5,8,2,8,1,7,1,8,0,9,
%T A187426 4,1,1,3,9,8,4,5,4,1,0,0,9,7,1,1,8,5,6,8,9,3,2,2,7,5,6,8,8,6,4,7,3,6,
%U A187426 9,7,6,8,5,9,0,5,4,8,7,7,5,1,4
%N A187426 Decimal expansion of (3-phi)^2 = 10 - 5*phi where phi is the golden ratio.
%C A187426 This is an integer in Q(sqrt(5)). - _Wolfdieter Lang_, Jan 07 2018
%H A187426 Ivan Panchenko, <a href="/A187426/b187426.txt">Table of n, a(n) for n = 1..1000</a>
%H A187426 <a href="/index/Al#algebraic_02">Index entries for algebraic numbers, degree 2</a>.
%F A187426 (3-phi)^2 = 5/phi^2 = 10 - 5*phi.
%F A187426 Smaller root of x^2 - 15x + 25 = 0.
%F A187426 Equals 10*A187798-5. - _R. J. Mathar_, Feb 08 2023
%e A187426 1.909830...
%t A187426 RealDigits[(3-GoldenRatio)^2,10,120][[1]] (* _Harvey P. Dale_, Jun 30 2017 *)
%o A187426 (PARI) (15-5*sqrt(5))/2 \\ _Charles R Greathouse IV_, Aug 31 2013
%o A187426 (PARI) polrootsreal(x^2-15*x+25)[1] \\ _Charles R Greathouse IV_, Feb 04 2025
%Y A187426 Cf. A226765.
%Y A187426 Apart from the first digit the same as A187798.
%K A187426 nonn,cons
%O A187426 1,2
%A A187426 _Joost Gielen_, Aug 30 2013
%E A187426 Corrected and extended by _Charles R Greathouse IV_, Aug 31 2013