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 A228172 #33 Feb 28 2017 22:59:30 %S A228172 1,3,6,9,14,19,24,31,39,48,56,65,77,88,101,113,127,141,157,174,189, %T A228172 208,226,244,266,287,309,330,353,378,401,428,454,482,511,537,568,596, %U A228172 630,662,692,726,760,797,833,867,905,942,982,1023,1065,1106,1146,1189,1231,1278,1322,1369,1414,1462,1512 %N A228172 Number of integer pairs (x,y) such that 0<=y<=x, x>0, and x^2+y^2<=n^2. %C A228172 This corresponds to points of positive norm less than or equal to n on the square lattice, in the first quadrant, on or below the first diagonal. %F A228172 a(n) = A211340 (n) + n . [_Joerg Arndt_, Aug 19 2013] %Y A228172 Cf. A211340 (version excluding the cases with y=0). %K A228172 nonn %O A228172 1,2 %A A228172 _Olivier Gérard_, Aug 17 2013