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.

A356869 Decimal expansion of 4 / sqrt(5).

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%I A356869 #56 Sep 09 2022 23:37:48
%S A356869 1,7,8,8,8,5,4,3,8,1,9,9,9,8,3,1,7,5,7,1,2,7,3,3,8,9,3,4,9,8,5,0,2,0,
%T A356869 9,8,8,3,5,2,4,9,4,6,8,7,6,8,9,2,2,0,5,7,9,4,1,6,7,1,7,7,9,6,3,2,8,4,
%U A356869 1,6,7,4,0,5,1,0,2,4,3,9,1,9,5,3,1,5,3,1,5,2,6,7,0,3,0,2,5
%N A356869 Decimal expansion of 4 / sqrt(5).
%C A356869 The area of a golden rectangle inscribed in a unit circle.
%C A356869 The width and height of the rectangle are:
%C A356869   W = sqrt(2 - 2 / sqrt(5)) = A179290.
%C A356869   H = sqrt(2 + 2 / sqrt(5)) = A121570.
%F A356869 Equals [1; 1, 3, 1, 2] (periodic continued fraction expansion). - _Peter Luschny_, Sep 02 2022
%F A356869 Equals 1/A204188. - _Alois P. Heinz_, Sep 02 2022
%e A356869 1.7888543819998317...
%p A356869 parse(substring(convert(evalf(4 / sqrt(5), 105), string), 1..98));
%t A356869 RealDigits[4 / Sqrt[5], 10, 105][[1]][[Range[1, 97]]]
%o A356869 (MATLAB) cell2mat(struct2cell(struct(vpa(4 / sqrt(5), 105)))); ans(1:98)
%Y A356869 Cf. A121570, A179290, A204188.
%K A356869 nonn,cons,easy
%O A356869 1,2
%A A356869 _Michal Paulovic_, Sep 01 2022