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.
%I A204188 #26 Dec 04 2018 07:42:12
%S A204188 5,5,9,0,1,6,9,9,4,3,7,4,9,4,7,4,2,4,1,0,2,2,9,3,4,1,7,1,8,2,8,1,9,0,
%T A204188 5,8,8,6,0,1,5,4,5,8,9,9,0,2,8,8,1,4,3,1,0,6,7,7,2,4,3,1,1,3,5,2,6,3,
%U A204188 0,2,3,1,4,0,9,4,5,1,2,2,4,8,5,3,6,0,3,6,0,2,0,9,4,6,9,5,5,6,8,7
%N A204188 Decimal expansion of sqrt(5)/4.
%C A204188 Equals Product_{n>=1} (1 - 1/A000032(2^n)).
%C A204188 Essentially the same as A019863 and A019827. - _R. J. Mathar_, Jan 16 2012
%C A204188 The value is the distance of the W point of the Wigner-Seitz cell of the body-centered cubic lattice (that is the Brioullin zone of the face-centered cubic lattice) to its four nearest neighbors. Let the points of the simple cubic lattice be at (1,0,0), (0,1,0), (1,0,0) etc and the point in the cube center at (1/2, 1/2, 1/2). Then W is at (0, 1/4, 1/2) [or any of the 24 symmetry related positions like (0, 3/4, 1/2), (0, 1/2, 1/4) etc.], and the four lattice points closest to W are at (-1/2, 1/2, 1/2), (0,0,0), (1/2, 1/2, 1/2) and (0,0,1). - _R. J. Mathar_, Aug 19 2013
%H A204188 J. Sondow, <a href="http://arxiv.org/abs/1106.4246">Evaluation of Tachiya's algebraic infinite products involving Fibonacci and Lucas numbers</a>, Diophantine Analysis and Related Fields 2011 - AIP Conference Proceedings, vol. 1385, pp. 97-100.
%H A204188 Y. Tachiya, <a href="http://dx.doi.org/10.1016/j.jnt.2006.11.006">Transcendence of certain infinite products</a>, J. Number Theory 125 (2007), 182-200.
%H A204188 Wikipedia, <a href="http://en.wikipedia.org/wiki/Brillouin_zone">Brillouin zone</a>
%F A204188 Equals sqrt(5)/4 = (-1 + 2*phi)/4, with the golden section phi from A001622.
%F A204188 Equals 5*A020837.
%e A204188 0.5590169943749474241022934171828190588601545899028814310677243113526302...
%p A204188 evalf(sqrt(5)/4);
%t A204188 RealDigits[Sqrt[5]/4, 10, 100][[1]] (* _Amiram Eldar_, Dec 04 2018 *)
%o A204188 (PARI) sqrt(5)/4 \\ _Charles R Greathouse IV_, Apr 21 2016
%Y A204188 Cf. A001622, A002163.
%K A204188 nonn,cons
%O A204188 0,1
%A A204188 _Jonathan Sondow_, Jan 14 2012