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 A243214 #7 Jun 13 2014 12:14:09 %S A243214 0,63,1566,13971,77124,319206,1083723,3181401,8344854,20006349, %T A243214 44548227,93248628,185176866,351410664,640972980,1129067352, %U A243214 1928196432,3203016813 %N A243214 Number of 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 A243214 a(n) = (n^10 + 5*n^9 - 10*n^8)/3840 + O(n^7) %Y A243214 Cf. A243211, A243210, A000217, A050534, A243212, A243213. %K A243214 nonn,more %O A243214 3,2 %A A243214 _Heinrich Ludwig_, Jun 10 2014