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 A385264 #10 Jul 03 2025 01:16:39 %S A385264 2,0,5,8,4,8,1,3,8,1,1,7,9,6,3,9,9,0,0,2,0,3,6,5,2,6,9,2,9,9,3,5,9,2, %T A385264 7,8,9,8,9,4,1,1,4,0,3,7,6,4,2,8,6,4,5,8,9,4,7,3,4,5,8,6,4,9,0,2,2,6, %U A385264 5,6,2,2,1,0,9,4,3,4,6,4,1,5,5,7,6,0,5,2,0,6 %N A385264 Decimal expansion of the volume of a gyroelongated pentagonal birotunda with unit edge. %C A385264 The gyroelongated pentagonal birotunda is Johnson solid J_48. %H A385264 Paolo Xausa, <a href="/A385264/b385264.txt">Table of n, a(n) for n = 2..10000</a> %H A385264 Wikipedia, <a href="https://en.wikipedia.org/wiki/Gyroelongated_pentagonal_birotunda">Gyroelongated pentagonal birotunda</a>. %F A385264 Equals (45 + 17*sqrt(5) + 5*sqrt(2*(sqrt(650 + 290*sqrt(5)) - sqrt(5) - 1)))/6 = (45 + 17*A002163 + 5*sqrt(2*(sqrt(650 + 290*A002163) - A002163 - 1)))/6. %F A385264 Equals the largest real root of 6561*x^8 - 393660*x^7 + 9316620*x^6 - 108207900*x^5 + 601832025*x^4 - 1417189500*x^3 + 965841750*x^2 + 597667500*x - 668786875. %e A385264 20.5848138117963990020365269299359278989411403764... %t A385264 First[RealDigits[(45 + 17*# + 5*Sqrt[2*(Sqrt[650 + 290*#] - # - 1)])/6 & [Sqrt[5]], 10, 100]] (* or *) %t A385264 First[RealDigits[PolyhedronData["J48", "Volume"], 10, 100]] %Y A385264 Cf. A385488 (surface area). %Y A385264 Cf. A002163, A384283, A385260, A385262. %K A385264 nonn,cons,easy %O A385264 2,1 %A A385264 _Paolo Xausa_, Jun 30 2025