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A272535 Decimal expansion of the edge length of a regular 16-gon with unit circumradius. 4

%I

%S 3,9,0,1,8,0,6,4,4,0,3,2,2,5,6,5,3,5,6,9,6,5,6,9,7,3,6,9,5,4,0,4,4,4,

%T 8,1,8,5,5,3,8,3,2,3,5,5,0,3,9,0,9,6,1,5,5,0,9,0,0,4,1,7,8,9,8,9,5,2,

%U 6,6,3,7,5,7,1,8,4,9,1,6,0,4,5,0,6,5,0,6,1,8,4,6,8,1,8,0,7,6,3,4,6,1,9,8,4

%N Decimal expansion of the edge length of a regular 16-gon with unit circumradius.

%C Like all m-gons with m equal to a power of 2 (see A003401 and A000079), this is a constructible number.

%H Stanislav Sykora, <a href="/A272535/b272535.txt">Table of n, a(n) for n = 0..2000</a>

%H Mauro Fiorentini, <a href="http://www.bitman.name/math/article/264">Construibili (numeri)</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ConstructibleNumber.html">Constructible Number</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Constructible_number">Constructible number</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Regular_polygon">Regular polygon</a>

%F Equals 2*sin(Pi/m) for m=16. Equals also sqrt(2-sqrt(2+sqrt(2))).

%e 0.390180644032256535696569736954044481855383235503909615509004...

%t RealDigits[N[2Sin[Pi/16], 100]][[1]] (* _Robert Price_, May 02 2016*)

%o (PARI) 2*sin(Pi/16)

%Y Cf. A000079, A003401.

%Y Edge lengths of other constructible m-gons: A002194 (m=3), A002193 (4), A182007 (5), A101464 (8), A094214 (10), A101263 (12), A272534 (15), A228787 (17), A272536 (20).

%K nonn,cons,easy

%O 0,1

%A _Stanislav Sykora_, May 02 2016

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Last modified January 17 23:41 EST 2019. Contains 319251 sequences. (Running on oeis4.)