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 A384872 #12 Jun 12 2025 12:59:56 %S A384872 2,3,5,3,8,5,3,2,3,3,2,5,0,6,0,5,8,3,1,0,0,4,1,0,0,7,6,2,2,3,6,7,2,8, %T A384872 8,5,7,1,8,8,7,1,3,8,8,9,1,8,6,0,3,1,5,6,5,9,6,5,8,9,3,9,1,2,2,1,1,1, %U A384872 8,3,1,7,5,8,8,7,0,7,6,3,7,5,8,3,8,1,3,8,6,8 %N A384872 Decimal expansion of the surface area of a pentagonal orthocupolarotunda with unit edge. %C A384872 The pentagonal orthocupolarotunda is Johnson solid J_32. %C A384872 Also the surface area of a pentagonal gyrocupolarotunda (Johnson solid J_33) with unit edge. %H A384872 Paolo Xausa, <a href="/A384872/b384872.txt">Table of n, a(n) for n = 2..10000</a> %H A384872 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentagonal_gyrocupolarotunda">Pentagonal gyrocupolarotunda</a>. %H A384872 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentagonal_orthocupolarotunda">Pentagonal orthocupolarotunda</a>. %F A384872 Equals 5 + (15/4)*sqrt(3) + (7/4)*sqrt(25 + 10*sqrt(5)) = 5 + (15/4)*A002194 + (7/4)*sqrt(25 + 10*A002163). %F A384872 Equals the largest root of 256*x^8 - 10240*x^7 + 57600*x^6 + 1856000*x^5 - 21756000*x^4 + 6320000*x^3 + 484812500*x^2 - 364125000*x - 342171875. %e A384872 23.538532332506058310041007622367288571887138891860... %t A384872 First[RealDigits[5 + 15/4*Sqrt[3] + 7/4*Sqrt[25 + 10*Sqrt[5]], 10, 100]] (* or *) %t A384872 First[RealDigits[PolyhedronData["J32", "SurfaceArea"], 10, 100]] %Y A384872 Cf. A384871 (volume). %Y A384872 Cf. A002163, A002194, A384284, A384286, A384625. %K A384872 nonn,cons,easy %O A384872 2,1 %A A384872 _Paolo Xausa_, Jun 11 2025