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 A387149 #10 Aug 22 2025 02:44:01 %S A387149 2,2,2,6,1,9,5,4,3,6,9,0,2,4,2,9,8,0,9,5,9,9,1,8,8,8,3,1,5,4,9,7,6,4, %T A387149 0,7,4,7,0,4,6,7,1,2,4,5,5,0,9,0,2,1,1,0,9,3,2,2,1,8,7,0,3,8,8,7,0,4, %U A387149 3,5,8,2,3,6,7,2,1,7,8,1,0,8,6,4,0,6,8,8,5,2 %N A387149 Decimal expansion of the second largest dihedral angle, in radians, in a gyroelongated square pyramid (Johnson solid J_10). %C A387149 This is the dihedral angle between adjacent triangular faces in the square antiprism part of the solid. %C A387149 Also the analogous dihedral angle in a gyroelongated square bipyramid (Johnson solid J_17). %H A387149 Paolo Xausa, <a href="/A387149/b387149.txt">Table of n, a(n) for n = 1..10000</a> %H A387149 Wikipedia, <a href="https://en.wikipedia.org/wiki/Gyroelongated_square_bipyramid">Gyroelongated square bipyramid</a>. %H A387149 Wikipedia, <a href="https://en.wikipedia.org/wiki/Gyroelongated_square_pyramid">Gyroelongated square pyramid</a>. %F A387149 Equals arccos((1 - 2*sqrt(2))/3) = arccos((1 - A010466)/3). %e A387149 2.2261954369024298095991888315497640747046712455090... %t A387149 First[RealDigits[ArcCos[(1 - Sqrt[8])/3], 10, 100]] (* or *) %t A387149 First[RealDigits[RankedMax[Union[PolyhedronData["J10", "DihedralAngles"]], 2], 10, 100]] %Y A387149 Cf. other J_10 dihedral angles: A156546, A387148, A387150. %Y A387149 Cf. A179638 (J_10 volume), A374948 (J_10 surface area). %Y A387149 Cf. A010466. %K A387149 nonn,cons,easy %O A387149 1,1 %A A387149 _Paolo Xausa_, Aug 19 2025