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 A234352 #13 Apr 19 2016 07:47:22 %S A234352 2,24,153,713,2557,7661,20055,47153,101821,205322,390580,707708, %T A234352 1229969,2060777,3344487 %N A234352 Number of non-equivalent (mod D_3) ways to arrange 4 indistinguishable points on a triangular grid of side n so that no three points are collinear. %C A234352 Column 4 of triangle A234350. %C A234352 Without the restriction "non-equivalent (mod D_3)" the numbers are given by A194132. %e A234352 There are a(3) = 2 non-equivalent ways to arrange 4 indistinguishable points (x) on a triangular grid of side 3: %e A234352 x . %e A234352 x x x x %e A234352 . x . x . x %Y A234352 Cf. A234350, A194132 %Y A234352 Arranging 3 points: A234351 %Y A234352 Arranging 5 points: A234353 %Y A234352 Arranging 6 points: A234354 %K A234352 nonn,more %O A234352 3,1 %A A234352 _Heinrich Ludwig_, Dec 30 2013 %E A234352 a(14)-a(17) from _Heinrich Ludwig_, Apr 19 2016