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 A268580 #21 Feb 16 2025 08:33:30 %S A268580 3,9,3,9,1,2,7,7,5,5,0,0,8,0,4,5,3,5,7,0,2,8,2,1,6,2,5,4,6,6,3,7,5,1, %T A268580 3,4,1,3,0,7,1,7,8,1,4,0,7,3,1,7,3,7,2,3,5,5,1,6,8,0,0,4,9,8,9,7,9,9, %U A268580 3,2,6,6,8,7,2,3,1,3,1,9,4,9,1,6,4,5,5,5,0,8,9,8,0,1,6,1,6,7,4,7,9,7,4,5,9,0,7,6,0,4,7,2,5,8,7,7,2,4,0,3 %N A268580 Decimal expansion of sqrt(Pi + Pi*sqrt(Pi + Pi*sqrt(Pi + ...))). %H A268580 G. C. Greubel, <a href="/A268580/b268580.txt">Table of n, a(n) for n = 1..5000</a> %H A268580 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Pi.html">Pi</a> %H A268580 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/NestedRadical.html">Nested Radical</a> %F A268580 Equals (Pi + sqrt(Pi^2 + 4*Pi))/2. %e A268580 3.9391277550080453570282162546637513413... %t A268580 RealDigits[(Pi + Sqrt[Pi^2 + 4 Pi])/2, 10, 120][[1]] %o A268580 (PARI) (Pi + sqrt(Pi^2 + 4*Pi))/2 \\ _Michel Marcus_, Feb 21 2016 %Y A268580 Cf. A000796, A100941, A189970. %K A268580 nonn,cons %O A268580 1,1 %A A268580 _Ilya Gutkovskiy_, Feb 21 2016