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 A387609 #10 Sep 05 2025 11:34:23 %S A387609 2,2,1,5,9,4,1,9,0,6,4,8,7,8,0,7,1,4,6,9,8,6,9,3,5,8,8,9,9,1,9,6,2,8, %T A387609 9,1,6,8,0,3,7,5,9,1,9,9,9,7,5,9,1,2,1,8,4,1,5,8,5,5,2,7,5,0,5,2,6,9, %U A387609 3,4,1,5,2,3,0,6,8,2,0,5,4,7,3,6,8,1,8,3,8,3 %N A387609 Decimal expansion of the fifth largest (second smallest) dihedral angle, in radians, in a gyroelongated pentagonal cupola (Johnson solid J_24). %C A387609 This is the dihedral angle between a triangular face and a square face at the edge where the antiprism and cupola parts of the solid meet. %C A387609 Also the analogous dihedral angle in a gyroelongated pentagonal bicupola and gyroelongated pentagonal cupolarotunda (Johnson solids J_46 and J_47, respectively). %H A387609 Paolo Xausa, <a href="/A387609/b387609.txt">Table of n, a(n) for n = 1..10000</a> %H A387609 Polytope Wiki, <a href="https://polytope.miraheze.org/wiki/Gyroelongated_pentagonal_bicupola">Gyroelongated pentagonal bicupola</a>. %H A387609 Polytope Wiki, <a href="https://polytope.miraheze.org/wiki/Gyroelongated_pentagonal_cupola">Gyroelongated pentagonal cupola</a>. %H A387609 Polytope Wiki, <a href="https://polytope.miraheze.org/wiki/Gyroelongated_pentagonal_cupolarotunda">Gyroelongated pentagonal cupolarotunda</a>. %H A387609 Wikipedia, <a href="https://en.wikipedia.org/wiki/Gyroelongated_pentagonal_bicupola">Gyroelongated pentagonal bicupola</a>. %H A387609 Wikipedia, <a href="https://en.wikipedia.org/wiki/Gyroelongated_pentagonal_cupola">Gyroelongated pentagonal cupola</a>. %H A387609 Wikipedia, <a href="https://en.wikipedia.org/wiki/Gyroelongated_pentagonal_cupolarotunda">Gyroelongated pentagonal cupolarotunda</a>. %F A387609 Equals arctan(2)/2 + arccos((sqrt(5 + 2*sqrt(5)) - sqrt(5) - 1)/sqrt(3)) = A195693 + arccos((sqrt(5 + A010476) - A002163 - 1)/A002194). %F A387609 Equals A195693 + A387610. %e A387609 2.2159419064878071469869358899196289168037591999759... %t A387609 First[RealDigits[ArcTan[2]/2 + ArcCos[(Sqrt[5 + Sqrt[20]] - Sqrt[5] - 1)/Sqrt[3]], 10, 100]] (* or *) %t A387609 First[RealDigits[RankedMax[Union[PolyhedronData["J24", "DihedralAngles"]], 5], 10, 100]] %Y A387609 Cf. other J_24 dihedral angles: A377995, A377996, A387607, A387608, A387610. %Y A387609 Cf. A384283 (J_24 volume), A384284 (J_24 surface area). %Y A387609 Cf. A385260 (J_46 volume), A385261 (J_46 surface area). %Y A387609 Cf. A385262 (J_47 volume), A385263 (J_47 surface area). %Y A387609 Cf. A002163, A002194, A010476, A195693. %K A387609 nonn,cons,easy,new %O A387609 1,1 %A A387609 _Paolo Xausa_, Sep 05 2025