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%I #24 May 18 2021 03:00:55
%S 1,5,2,3,6,2,7,0,8,6,2,0,2,4,9,2,1,0,6,2,7,7,6,8,3,9,3,5,9,5,4,2,1,6,
%T 6,2,7,2,8,4,9,3,6,3,8,3,4,0,1,1,9,3,4,7,8,1,3,8,6,9,0,9,0,9,4,5,7,9,
%U 2,1,6,6,2,8,9,5,8,8,4,1,0,6,8,9,2,6,6,4,2,2,7,4,6,4,7,1,3,9,4,2,8,1,1,2,4
%N Decimal expansion of the Hausdorff dimension of the Heighway-Harter dragon curve boundary.
%C The value for 'twindragon' is the same.
%H Stanislav Sykora, <a href="/A272031/b272031.txt">Table of n, a(n) for n = 1..2000</a>
%H Angel Chang and Tianrong Zhang, <a href="http://poignance.coiraweb.com/math/Fractals/Dragon/Bound.html">On the Fractal Structure of the Boundary of Dragon Curve</a>, Journal of Recreational Mathematics, volume 30, number 1, 1999-2000, pages 9-22. See also the <a href="https://angelxuanchang.github.io/pubs/dragonbound.pdf">pdf</a> version.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DragonCurve.html">Dragon curve</a>.
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Dragon_curve">Dragon curve</a>.
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/List_of_fractals_by_Hausdorff_dimension">List of fractals by Hausdorff dimension</a>.
%F Equals log_2((1+(73+6*sqrt(87))^(1/3)+(73-6*sqrt(87))^(1/3))/3).
%F From _Kevin Ryde_, Dec 06 2019: (Start)
%F Equals 2*log(A289265)/log(2) [Chang and Zhang, equation 9].
%F Equals log(A289265)/log(sqrt(2)). (End)
%e 1.5236270862024921062776839359542166272849363834011934781386909094...
%t RealDigits[Log2[(1 + (73+6*Sqrt[87])^(1/3) + (73-6*Sqrt[87])^(1/3))/3], 10, 100][[1]] (* _Amiram Eldar_, May 18 2021 *)
%o (PARI) log((1+(73+6*sqrt(87))^(1/3)+(73-6*sqrt(87))^(1/3))/3)/log(2)
%Y Cf. A014577, A191689 (Levy dragon), A327620 (tame twin-dragon).
%K nonn,cons
%O 1,2
%A _Stanislav Sykora_, Apr 18 2016
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