# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a239572 Showing 1-1 of 1 %I A239572 #12 Mar 08 2017 11:55:57 %S A239572 1,1,2,2,1,3,6,6,1,4,16,32,24,7,1,5,32,113,200,176,66,6,7,60,329,1053, %T A239572 1976,2096,1162,302,34,2,8,100,790,3932,12565,25676,32963,25638,11294, %U A239572 2493,222,7,10,160,1702,11988,57275,187984,425329,658608,684671,462519 %N A239572 Triangle T(n, k) = Numbers of non-equivalent (mod D_3) ways to place k points on a triangular grid of side n so that no two of them are adjacent. Triangle read by rows. %C A239572 Triangle T(n, k) is irregularly shaped: 1 <= k <= A239438(n). First row corresponds to n = 1. %C A239572 The maximal number of points that can be placed on a triangular grid of side n so that no two of them are adjacent is given by A239438(n). %C A239572 Without the restriction "non-equivalent (mod D_3)" numbers are given by A239567. %H A239572 Heinrich Ludwig, Table of n, a(n) for n = 1..136 %e A239572 Triangle begins %e A239572 1; %e A239572 1; %e A239572 2, 2, 1; %e A239572 3, 6, 6, 1; %e A239572 4, 16, 32, 24, 7, 1; %e A239572 5, 32, 113, 200, 176, 66, 6; %e A239572 7, 60, 329, 1053, 1976, 2096, 1162, 302, 34, 2; %e A239572 8, 100, 790, 3932, 12565, 25676, 32963, 25638, 11294, 2493, 222, 7; %Y A239572 Cf. A239438, A239567. %Y A239572 Column 1 is A001399, %Y A239572 Column 2 is A032091, %Y A239572 Column 3 is A239573, %Y A239572 Column 4 is A239574, %Y A239572 Column 5 is A239575, %Y A239572 Column 6 is A279446. %K A239572 nonn,tabf %O A239572 1,3 %A A239572 _Heinrich Ludwig_, Mar 22 2014 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE