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 A210641 #13 Feb 04 2016 03:44:42
%S A210641 1,3,7,5,-1,10,19,3,-2,10,15,18,5,7,32,8,-11,11,21,18,14,34,29,-1,-7,
%T A210641 -9,32,31,-2,37,51,16,-7,5,17,28,20,6,40,1,-15,41,49,32,14,45,50,7,
%U A210641 -28,-18,22,25,4,31,81,34,36,36,13,37,-12,11,58,8,-36,10,55
%N A210641 A117609(n)-A210639(n): Difference between number of lattice points in the ball x^2+y^2+z^2 <= n and the volume of this ball rounded to the nearest integer.
%C A210641 Record values are listed in A000223, and A000092 gives the corresponding indices. Strictly speaking, these are defined using the absolute values, but it appears they always occur at positive elements.
%t A210641 a[n_] := Sum[SquaresR[3, k], {k, 0, n}] - Round[(4/3)*Pi*n^(3/2)]; Table[a[n], {n, 0, 100}] (* _Jean-François Alcover_, Feb 04 2016 *)
%o A210641 (PARI) A210641(n)=A117609(n)-A210639(n)
%K A210641 sign
%O A210641 0,2
%A A210641 _M. F. Hasler_, Mar 26 2012