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 A380863 #8 Feb 08 2025 03:43:41 %S A380863 2,0,6,4,1,7,7,8,2,3,8,3,9,0,7,2,1,3,4,9,3,0,7,6,7,8,6,4,9,8,6,9,7,3, %T A380863 0,0,6,9,9,7,0,5,1,3,6,5,3,2,7,4,7,0,8,2,1,9,6,6,9,4,4,2,8,6,3,4,8,2, %U A380863 2,1,7,1,4,0,7,1,3,8,7,1,6,7,8,4,1,5,5,7,8,3 %N A380863 Decimal expansion of the obtuse vertex angle, in radians, in a deltoidal hexecontahedron face. %C A380863 A deltoidal hexecontahedron face is a kite with one smallest acute angle (A380861), two largest acute angles (A380862) and one obtuse angle (this constant). %H A380863 Paolo Xausa, <a href="/A380863/b380863.txt">Table of n, a(n) for n = 1..10000</a> %H A380863 Wikipedia, <a href="https://en.wikipedia.org/wiki/Deltoidal_hexecontahedron">Deltoidal hexecontahedron</a>. %F A380863 Equals arccos((-5 - 2*sqrt(5))/20) = arccos((-5 - 2*A002163)/20). %F A380863 Equals 2*Pi - A380861 - 2*A380862. %e A380863 2.0641778238390721349307678649869730069970513653... %t A380863 First[RealDigits[ArcCos[(-5 - 2*Sqrt[5])/20], 10, 100]] %Y A380863 Cf. A002163, A379385, A379386, A379387, A379388, A379389, A380861, A380862. %K A380863 nonn,cons,easy %O A380863 1,1 %A A380863 _Paolo Xausa_, Feb 07 2025