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 A053459 #7 Mar 23 2022 12:51:03 %S A053459 0,0,4,8,14,22,30,42,60,74,92,108,130,148,178,206,230,262,288,324,364, %T A053459 400,442,480,522,562,614,662,712,764,812,868,922,988,1050,1106,1176, %U A053459 1234,1312,1376,1452,1528,1598,1678,1750,1838,1920,2006,2092,2172,2266 %N A053459 Open disk numbers (version 4): a(n) is the number of points (i+j/2,j*sqrt(3)/2), i,j integers (triangular grid) contained in an open disk of diameter n, centered at (1/2,0). %C A053459 a(n)/(n/2)^2 -> Pi*2/sqrt(3). %Y A053459 Cf. A053417, A053456, A053457, A053458. %K A053459 easy,nonn %O A053459 0,3 %A A053459 Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Jan 13 2000