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 A137915 #16 Feb 16 2025 08:33:07 %S A137915 7,0,5,2,8,7,7,9,3,6,5,5,0,9,3,0,8,6,3,0,7,5,4,0,0,0,6,6,0,0,3,7,5,6, %T A137915 4,0,3,6,9,9,3,1,5,6,8,9,9,0,9,2,0,5,1,7,1,1,8,2,8,8,9,3,6,4,3,9,6,0, %U A137915 2,5,3,5,6,1,9,3,9,6,0,4,4,3,6,6,3,8,1,2,8,7,1,1,6,3,9,4,1,2,3,5,4,3,1,4,8 %N A137915 Decimal expansion of 180*arccos(1/3)/Pi. %C A137915 Dihedral angle in degrees of regular tetrahedron. %C A137915 Polar angle (or apex angle) of the cone that subtends exactly one third of the full solid angle. - _Stanislav Sykora_, Feb 20 2014 %H A137915 G. C. Greubel, <a href="/A137915/b137915.txt">Table of n, a(n) for n = 2..10001</a> %H A137915 Frank Jackson and Eric W. Weisstein, <a href="https://mathworld.wolfram.com/Tetrahedron.html">Tetrahedron</a> %H A137915 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DihedralAngle.html">Dihedral Angle</a> %F A137915 180*A137914/Pi = 180*arccos(1/3)/Pi. %e A137915 70.52877936550930863075400066003756403699315689909205171182889364396025356... %t A137915 RealDigits[180 ArcCos[1/3]/Pi,10,120][[1]] (* _Harvey P. Dale_, Jul 13 2013 *) %o A137915 (PARI) 180*acos(1/3)/Pi %o A137915 (Magma) SetDefaultRealField(RealField(100)); R:= RealField(); 180*Arccos(1/3)/Pi(R); // _G. C. Greubel_, Aug 20 2018 %Y A137915 Cf. A137914 (same in radians). %K A137915 cons,nonn %O A137915 2,1 %A A137915 _Rick L. Shepherd_, Feb 22 2008