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 A125851 #7 Mar 31 2012 10:29:10 %S A125851 0,3,6,12,19,30,40,54,69,87,102,123,149,174,198,225,253,287,313,354, %T A125851 396,435 %N A125851 Number of points in a hexagonal lattice covered by a circular disk of diameter n if the center of the circle is chosen such that the disk covers the minimum possible number of lattice points. %C A125851 a(n)<=min(A053416(n),A053479(n),A053417(n)) %H A125851 <a href="/index/Aa#A2">Index entries for sequences related to A2 = hexagonal = triangular lattice</a> %H A125851 Hugo Pfoertner, <a href="http://www.randomwalk.de/sequences/a125851.pdf">Minimal number of points in the hexagonal lattice covered by circular disks.</a> Illustrations. %Y A125851 Cf. A053416, A053479, A053417, A125852. The corresponding sequences for the square lattice and the honeycomb net are A123689 and A127405, respectively. %K A125851 more,nonn %O A125851 1,2 %A A125851 _Hugo Pfoertner_, Jan 07 2007, Feb 11 2007