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 A047077 #23 Mar 31 2018 14:41:27
%S A047077 5,12,20,24,36,44,40,52,60,68,72,68,92,96,100,100,108,120,124,132,128,
%T A047077 148,140,144,172,180,180,168,180,204,192,212,204,220,240,212,244,232,
%U A047077 268,260,248,276,268,292,288,276,300,296,316,324,348,336,324,348,336
%N A047077 Number of pairs of integers (x,y) with n^2 <= x^2+y^2 <= (n+1)^2.
%C A047077 Number of integer Cartesian grid points covered by a ring around the origin with width 1 and outer radius n. Also, number of Gaussian integers z=a+bi satisfying n-1 <= |z| <= n. - _Ralf Stephan_, Nov 28 2013
%H A047077 T. D. Noe, <a href="/A047077/b047077.txt">Table of n, a(n) for n = 0..1000</a>
%H A047077 <a href="/index/Ga#gaussians">Index entries for Gaussian integers and primes</a>
%F A047077 a(n) = A000328(n+1) - A051132(n).
%t A047077 a[n_] := Sum[SquaresR[2, k], {k, n^2, (n+1)^2}]; Table[a[n], {n, 0, 54}] (* _Jean-François Alcover_, Oct 15 2012 *)
%Y A047077 Cf. A000328, A051132, A077770.
%K A047077 easy,nice,nonn
%O A047077 0,1
%A A047077 Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Jan 26 2000