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 A240442 #11 Apr 25 2014 16:17:14 %S A240442 0,39,1194,11259,64776,275805,957516,2859768,7606821,18444537, %T A240442 41458599,87464157,174846963,333687378,611613150,1081890447 %N A240442 Number of ways to place 5 points on a triangular grid of side n so that no three of these points are vertices of an equilateral triangle of any orientation. %F A240442 a(n) = (n^10 + 5*n^9 - 30*n^8 - 150*n^7)/3840 + O(n^6). %Y A240442 Cf. A240439, A240440, A240441. %K A240442 nonn,more %O A240442 3,2 %A A240442 _Heinrich Ludwig_, Apr 08 2014 %E A240442 a(16)-a(18) from _Heinrich Ludwig_, Apr 25 2014