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 A380777 #10 Feb 03 2025 14:12:31 %S A380777 2,0,0,3,8,4,8,7,2,0,6,8,4,3,3,7,6,8,0,6,7,3,1,9,3,5,2,3,2,2,4,4,9,4, %T A380777 5,3,4,6,1,2,3,6,5,1,0,9,0,2,5,5,3,0,5,4,8,9,5,9,7,6,2,0,6,5,5,7,1,7, %U A380777 1,8,0,5,8,9,3,8,9,3,6,8,2,0,6,4,0,0,0,2,0,2 %N A380777 Decimal expansion of the obtuse vertex angles, in radians, in a pentagonal icositetrahedron face. %C A380777 A pentagonal icositetrahedron face is an irregular pentagon with one acute angle (A380776) and four (equal) obtuse angles (this constant). %H A380777 Paolo Xausa, <a href="/A380777/b380777.txt">Table of n, a(n) for n = 1..10000</a> %H A380777 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PentagonalIcositetrahedron.html">Pentagonal Icositetrahedron</a>. %H A380777 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentagonal_icositetrahedron">Pentagonal icositetrahedron</a>. %F A380777 Equals arccos((1 - A058265)/2). %F A380777 Equals arccos(c), where c is the real root of 4*x^3 - 4*x^2 + 1. %F A380777 Equals (3*Pi - A380776)/4. %e A380777 2.0038487206843376806731935232244945346123651090255... %t A380777 First[RealDigits[ArcCos[Root[4*#^3 - 4*#^2 + 1 &, 1]], 10, 100]] %Y A380777 Cf. A058265, A378823, A378824, A378825, A378826, A378827, A380775, A380776. %K A380777 nonn,cons,easy %O A380777 1,1 %A A380777 _Paolo Xausa_, Feb 03 2025