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 A075880 #20 Mar 12 2025 14:56:35 %S A075880 0,1,4,13,30,121,362,1232,1584,7121,17548,32649,37603,174926,437750, %T A075880 821432,1198677,5678338,14335447,27044791,43735981,209473053, %U A075880 531787054,1006745669,2097411347,8474384496,10122355701 %N A075880 Position of the circles around (0,0) that contain record numbers of lattice points in the list of all circles around (0,0) that pass through lattice points, ordered by increasing radius. %C A075880 The first terms of this sequence were given by James Buddenhagen in a sci.math posting on May 05 2002 entitled "Circle with 3 lattice points" %H A075880 James Buddenhagen, <a href="https://groups.google.com/d/msg/sci.math/Fp28xlllFXE/0xBmk4NwCPIJ">Circle with 3 lattice points</a>, thread in NG sci.math. %H A075880 Hugo Pfoertner, <a href="http://www.randomwalk.de/sequences/a075880.pdf">Asymptotic Behavior of A075880(n)</a> %F A075880 a(n) = k-1 for which A001481(k) = A071383(n). %F A075880 lim n ->infinity a(n) = k_LR * exp(n) / n^(1/2), where k_LR is the Landau-Ramanujan constant 0.764223653... (A064533) %e A075880 a(4)=13 because A001481(14) = A071383(4)=25. %Y A075880 Cf. A001481, A064533, A071383, A230656. %K A075880 nonn %O A075880 1,3 %A A075880 _Hugo Pfoertner_, Oct 16 2002 %E A075880 Minor edits to adjust formula and example for changes to offset of related sequences by _Ray Chandler_, Jan 13 2012