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 A380003 #9 Jan 13 2025 04:13:42 %S A380003 1,1,7,7,2,8,5,8,2,3,4,7,1,7,5,0,2,9,1,9,2,3,5,3,7,4,4,5,4,8,1,2,4,4, %T A380003 6,8,0,9,0,7,3,0,5,4,3,4,5,9,8,1,2,4,8,7,4,3,0,8,9,3,3,3,8,2,9,2,3,3, %U A380003 2,2,9,9,7,6,3,0,9,5,9,8,0,6,4,5,2,5,2,9,6,1 %N A380003 Decimal expansion of acute vertex angle, in radians, in a pentagonal hexecontahedron face. %C A380003 A pentagonal hexecontahedron face is an irregular pentagon with one acute angle (this constant) and four (equal) obtuse angles (A380004). %H A380003 Paolo Xausa, <a href="/A380003/b380003.txt">Table of n, a(n) for n = 1..10000</a> %H A380003 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PentagonalHexecontahedron.html">Pentagonal Hexecontahedron</a>. %H A380003 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentagonal_hexecontahedron">Pentagonal hexecontahedron</a>. %F A380003 Equals arccos(c), where c is the largest real root of 64*x^6 - 384*x^5 + 384*x^4 + 888*x^3 + 168*x^2 - 128*x - 31. %F A380003 Equals 3*Pi - 4*A380004. %e A380003 1.1772858234717502919235374454812446809073054345981... %t A380003 First[RealDigits[ArcCos[Root[64*#^6 - 384*#^5 + 384*#^4 + 888*#^3 + 168*#^2 - 128*# - 31 &, 4]], 10, 100]] %Y A380003 Cf. A379888 (surface area), A379889 (volume), A379890 (inradius), A379890 (midradius), A379892 (dihedral angle), A380002 (long/short edge length ratio), A380004 (face obtuse angles). %K A380003 nonn,cons,easy %O A380003 1,3 %A A380003 _Paolo Xausa_, Jan 12 2025