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 A234351 #14 Apr 19 2016 07:47:55 %S A234351 1,5,22,77,217,530,1149,2288,4231,7400,12322,19725,30486,45768,66917, %T A234351 95669 %N A234351 Number of non-equivalent (mod D_3) ways to arrange 3 indistinguishable points on a triangular grid of side n so that no three points are collinear. %C A234351 Column 3 of triangle A234350. %C A234351 Without the restriction "non-equivalent (mod D_3)" the numbers are given by A194131. %e A234351 There are a(3) = 5 non-equivalent ways to arrange 3 indistinguishable points (x) on a triangular grid of side 3: %e A234351 x . x x x %e A234351 . . x x x x . . x . %e A234351 x . x . x . . . . . x x . x . %Y A234351 Cf. A234350, A194131 %Y A234351 Arranging 4 points: A234352 %Y A234351 Arranging 5 points: A234353 %Y A234351 Arranging 6 points: A234354 %K A234351 nonn,more %O A234351 2,2 %A A234351 _Heinrich Ludwig_, Dec 30 2013 %E A234351 a(14)-a(17) from _Heinrich Ludwig_, Apr 19 2016