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 A384144 #9 May 23 2025 10:14:11 %S A384144 1,0,0,1,8,2,5,4,1,6,1,2,7,1,3,2,6,6,3,7,3,6,5,1,7,5,5,5,2,5,7,9,7,9, %T A384144 2,0,5,0,3,1,0,5,0,0,9,3,1,9,1,8,8,3,1,5,5,0,4,4,5,1,5,5,4,5,6,2,1,0, %U A384144 8,3,8,8,3,8,3,2,9,5,9,7,2,2,9,0,7,9,4,2,7,2 %N A384144 Decimal expansion of the volume of an elongated pentagonal cupola with unit edge. %C A384144 The elongated pentagonal cupola is Johnson solid J_20. %H A384144 Paolo Xausa, <a href="/A384144/b384144.txt">Table of n, a(n) for n = 2..10000</a> %H A384144 Wikipedia, <a href="https://en.wikipedia.org/wiki/Elongated_pentagonal_cupola">Elongated pentagonal cupola</a>. %F A384144 Equals (5 + 4*sqrt(5) + 15*sqrt(5 + 2*sqrt(5)))/6 = (5 + A010532 + 15*sqrt(5 + A010476))/6. %F A384144 Equals the largest root of 324*x^4 - 1080*x^3 - 20340*x^2 - 18600*x + 49975. %e A384144 10.0182541612713266373651755525797920503105009319... %t A384144 First[RealDigits[(5 + Sqrt[80] + 15*Sqrt[5 + Sqrt[20]])/6, 10, 100]] (* or *) %t A384144 First[RealDigits[PolyhedronData["J20", "Volume"], 10, 100]] %Y A384144 Cf. A179591 (surface area - 10). %Y A384144 Cf. A010476, A010532, A384138, A384140, A384213. %K A384144 nonn,cons,easy %O A384144 2,5 %A A384144 _Paolo Xausa_, May 22 2025