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 A385262 #9 Jun 30 2025 09:58:00 %S A385262 1,5,9,9,1,0,9,6,1,6,2,0,0,4,8,9,0,0,6,3,0,6,2,9,8,0,0,1,1,7,2,0,8,0, %T A385262 4,0,5,5,6,9,4,0,0,9,9,4,0,0,5,3,3,3,4,9,3,4,8,6,4,7,4,6,8,8,9,5,0,2, %U A385262 0,0,4,8,5,0,0,4,8,4,4,3,8,1,4,5,3,3,0,4,3,2 %N A385262 Decimal expansion of the volume of a gyroelongated pentagonal cupolarotunda with unit edge. %C A385262 The gyroelongated pentagonal cupolarotunda is Johnson solid J_47. %H A385262 Paolo Xausa, <a href="/A385262/b385262.txt">Table of n, a(n) for n = 2..10000</a> %H A385262 Wikipedia, <a href="https://en.wikipedia.org/wiki/Gyroelongated_pentagonal_cupolarotunda">Gyroelongated pentagonal cupolarotunda</a>. %F A385262 Equals (5/12)*(11 + 5*sqrt(5) + 2*sqrt(2*(sqrt(650 + 290*sqrt(5)) - sqrt(5) - 1))) = (5/12)*(11 + 5*A002163 + 2*sqrt(2*(sqrt(650 + 290*A002163) - A002163 - 1))). %F A385262 Equals the largest real root of 1679616*x^8 - 61585920*x^7 + 851472000*x^6 - 5108832000*x^5 + 4745790000*x^4 + 21346200000*x^3 - 29019375000*x^2 - 4576875000*x - 405859375. %e A385262 15.991096162004890063062980011720804055694009940053... %t A385262 First[RealDigits[5/12*(11 + 5*# + 2*Sqrt[2*(Sqrt[650 + 290*#] - # - 1)]) & [Sqrt[5]], 10, 100]] (* or *) %t A385262 First[RealDigits[PolyhedronData["J47", "Volume"], 10, 100]] %Y A385262 Cf. A385263 (surface area). %Y A385262 Cf. A002163, A384283, A385256, A385258, A385260. %K A385262 nonn,cons,easy %O A385262 2,2 %A A385262 _Paolo Xausa_, Jun 27 2025