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 A057962 #2 Mar 31 2012 10:24:40 %S A057962 4,12,16,24,32,44,52,60,68,76,80,88,96,112,120,124,140,148,156,164, %T A057962 172,180,188,192,208,216,232,240,248,256,268,276,284,300,308,316,332, %U A057962 348,360,368,376,384,392,400,408,424,432,440,448,460,468,484,492,500 %N A057962 Number of points (x,y) in square lattice with (x-1/2)^2+(y-1/2)^2 <= n. %C A057962 Always a multiple of 4. Useful for rasterizing circles. %D A057962 J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 106. %e A057962 a(2)=12 because (-1,0); (-1,1); (0,-1); (0,0); (0,1); (0,2); (1,-1); (1,0); (1,1); (1,2); (2,0); (2,1) are covered by any disc of radius between sqrt(2.5) and sqrt(4.5) and centered at (0.5,0.5). %Y A057962 Cf. A057961, A004018, A004020. Partial sums of A005883. %K A057962 easy,nonn %O A057962 1,1 %A A057962 _Ken Takusagawa_, Oct 15 2000