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A227260 Number of nX3 0,1 arrays indicating 2X2 subblocks of some larger (n+1)X4 binary array having a sum of two or less, with rows and columns of the latter in lexicographically nondecreasing order.

%I A227260 #6 Jul 23 2025 05:35:33
%S A227260 4,23,98,353,1111,3136,8065,19146,42385,88282,174361,328741,595043,
%T A227260 1038979,1757024,2887631,4625512,7239575,11095178,16681436,24644396,
%U A227260 35826978,51316667,72502032,101139243,139429856,190111239,256561119
%N A227260 Number of nX3 0,1 arrays indicating 2X2 subblocks of some larger (n+1)X4 binary array having a sum of two or less, with rows and columns of the latter in lexicographically nondecreasing order.
%C A227260 Column 3 of A227263
%H A227260 R. H. Hardin, <a href="/A227260/b227260.txt">Table of n, a(n) for n = 1..210</a>
%F A227260 Empirical: a(n) = (1/90720)*n^9 + (11/40320)*n^8 + (53/30240)*n^7 + (73/2880)*n^6 + (301/4320)*n^5 - (2683/5760)*n^4 + (448811/90720)*n^3 + (1613/1120)*n^2 - (83207/2520)*n + 33 for n>5
%e A227260 Some solutions for n=4
%e A227260 ..1..1..0....1..1..1....1..1..0....1..0..0....1..1..0....1..1..1....1..1..0
%e A227260 ..1..1..1....1..0..0....1..1..1....0..1..0....0..1..1....1..0..1....1..1..1
%e A227260 ..1..1..1....1..1..0....1..1..1....0..1..1....0..1..1....0..1..1....1..1..1
%e A227260 ..0..0..0....0..1..0....1..1..1....0..0..1....0..0..1....0..0..1....0..0..1
%K A227260 nonn
%O A227260 1,1
%A A227260 _R. H. Hardin_ Jul 04 2013