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 A243210 #7 Jun 13 2014 12:06:30 %S A243210 0,11,266,2344,12907,53307,180876,530654,1391647,3335627,7426885, %T A243210 15544434,30867669,58574800,106838511,188190111,321383808,533857914 %N A243210 Number of inequivalent (mod D_3) ways to place 5 points on a triangular grid of side n so that no three of them are vertices of an equilateral triangle with sides parallel to the grid. %F A243210 a(n) = (n^10 + 5*n^9 - 10*n^8 - 195*n^7)/23040 + O(n^6) %Y A243210 Cf. A243207, A243214, A001399, A227327, A243208, A243209. %K A243210 nonn,more %O A243210 3,2 %A A243210 _Heinrich Ludwig_, Jun 10 2014