cp's OEIS Frontend

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

%I A272535 #14 Sep 03 2025 04:03:12
%S A272535 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 A272535 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 A272535 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 A272535 Decimal expansion of the edge length of a regular 16-gon with unit circumradius.
%C A272535 Like all m-gons with m equal to a power of 2 (see A003401 and A000079), this is a constructible number.
%H A272535 Stanislav Sykora, <a href="/A272535/b272535.txt">Table of n, a(n) for n = 0..2000</a>
%H A272535 Mauro Fiorentini, <a href="http://www.bitman.name/math/article/264">Construibili (numeri)</a>
%H A272535 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ConstructibleNumber.html">Constructible Number</a>
%H A272535 Wikipedia, <a href="http://en.wikipedia.org/wiki/Constructible_number">Constructible number</a>
%H A272535 Wikipedia, <a href="http://en.wikipedia.org/wiki/Regular_polygon">Regular polygon</a>
%H A272535 <a href="/index/Al#algebraic_08">Index entries for algebraic numbers, degree 8</a>.
%F A272535 Equals 2*sin(Pi/m) for m=16, 2*A232738. Equals also sqrt(2-sqrt(2+sqrt(2))).
%e A272535 0.390180644032256535696569736954044481855383235503909615509004...
%t A272535 RealDigits[N[2Sin[Pi/16], 100]][[1]] (* _Robert Price_, May 02 2016*)
%o A272535 (PARI) 2*sin(Pi/16)
%Y A272535 Cf. A000079, A003401.
%Y A272535 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 A272535 nonn,cons,easy,changed
%O A272535 0,1
%A A272535 _Stanislav Sykora_, May 02 2016