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 A014202 #10 Jan 29 2018 02:49:16
%S A014202 0,1,1,2,3,3,3,5,5,6,6,6,7,9,9,9,10,10,10,12,12,14,14,14,14,15,15,16,
%T A014202 18,18,18,20,20,20,20,20,21,23,23,25,25,25,25,27,27,27,27,27,28,31,31,
%U A014202 31,33,33,33,33,33,35,35,35
%N A014202 Number of solutions to x^2 + x*y + y^2 <= n, excluding (0,0), divided by 6.
%F A014202 For n > 0, a(n) = Sum_{k=1..n} K(k,3)*floor(n/k) where K(x,y) is the Kronecker symbol. - _Benoit Cloitre_, Oct 31 2009
%o A014202 (PARI) a(n)=if(n<1,0,sum(k=1,n,kronecker(k,3)*floor(n/k))) \\ _Benoit Cloitre_, Oct 31 2009
%Y A014202 A014201/6. Cf. A014200.
%K A014202 nonn,easy
%O A014202 0,4
%A A014202 _N. J. A. Sloane_