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 A236556 #26 Feb 16 2025 08:33:21 %S A236556 1,3,5,9,3,4,7,6,3,7,8,1,6,4,8,7,7,4,8,3,8,5,5,7,0,0,5,3,5,6,7,0,5,6, %T A236556 2,6,5,5,5,2,9,7,8,7,6,1,3,2,9,8,3,2,2,8,5,7,2,7,6,9,5,8,4,9,9,5,9,6, %U A236556 6,3,5,5,4,6,5,9,3,9,3,6,4,5,8,4,3,0,6,3,1,7,0,0,0,0,7,9,0,4,5,1,4,0,8,5,1 %N A236556 Decimal expansion of the steradian solid angle subtended by one square facet of the cuboctahedron. %C A236556 Also the vertex solid angle of a regular octahedron. %H A236556 Stanislav Sykora, <a href="/A236556/b236556.txt">Table of n, a(n) for n = 1..2000</a> %H A236556 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Cuboctahedron.html">Cuboctahedron</a>. %H A236556 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SphericalPolygon.html">Spherical Polygon</a>. %H A236556 Wikipedia, <a href="http://en.wikipedia.org/wiki/Platonic_solid">Platonic solid</a>. %H A236556 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>. %F A236556 Equals 4*arcsin(1/3) = 4*A188615. %F A236556 Equals 2*Pi - 4*arcsin(2*sqrt(2)/3). - _Bradley Klee_, Oct 04 2018 %F A236556 8*A236555 + 6*this = 4*Pi. - _Bradley Klee_, Oct 04 2018 %e A236556 1.35934763781648774838557005356705626555297876132983228572769584995966... %p A236556 evalf(4*arcsin(1/3),100) ; # _R. J. Mathar_, Apr 26 2021 %t A236556 RealDigits[4*ArcSin[1/3], 10, 120][[1]] (* _Amiram Eldar_, May 22 2023 *) %o A236556 (PARI) 4*asin(1/3) %Y A236556 Cf. A188615, A236555. Icosidodecahedron: A319881, A319883. Vertex Angles: A019669, A236557, A236558. %K A236556 nonn,cons,easy %O A236556 1,2 %A A236556 _Stanislav Sykora_, Jan 28 2014 %E A236556 Definition corrected by _Bradley Klee_, Oct 04 2018