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 A380861 #13 Feb 08 2025 03:43:57 %S A380861 1,1,8,3,0,3,6,7,2,8,4,2,0,0,8,3,4,1,4,7,9,0,1,3,6,1,8,6,7,9,9,8,8,7, %T A380861 8,6,5,0,5,4,8,2,0,6,6,8,3,6,8,4,0,6,3,5,9,7,6,6,7,9,2,8,5,3,3,5,5,6, %U A380861 4,0,7,3,1,4,3,9,9,2,7,5,3,9,6,4,9,4,8,8,0,3 %N A380861 Decimal expansion of the smallest acute vertex angle, in radians, in a deltoidal hexecontahedron face. %C A380861 A deltoidal hexecontahedron face is a kite with one smallest acute angle (this constant), two largest acute angles (A380862) and one obtuse angle (A380863). %H A380861 Paolo Xausa, <a href="/A380861/b380861.txt">Table of n, a(n) for n = 1..10000</a> %H A380861 Wikipedia, <a href="https://en.wikipedia.org/wiki/Deltoidal_hexecontahedron">Deltoidal hexecontahedron</a>. %F A380861 Equals arccos((9*sqrt(5) - 5)/40) = arccos((9*A002163 - 5)/40). %F A380861 Equals 2*Pi - 2*A380862 - A380863. %e A380861 1.1830367284200834147901361867998878650548206683684... %t A380861 First[RealDigits[ArcCos[(9*Sqrt[5] - 5)/40], 10, 100]] %Y A380861 Cf. A002163, A379385, A379386, A379387, A379388, A379389, A380862, A380863. %K A380861 nonn,cons,easy %O A380861 1,3 %A A380861 _Paolo Xausa_, Feb 06 2025