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A251221 Number of (n+1) X (1+1) 0..1 arrays with no 2 X 2 subblock having the minimum of its diagonal elements greater than the absolute difference of its antidiagonal elements.

%I A251221 #8 Feb 25 2018 09:17:38
%S A251221 14,49,171,597,2084,7275,25396,88654,309479,1080349,3771351,13165272,
%T A251221 45958169,160433700,560052166,1955065729,6824867819,23824682749,
%U A251221 83168718156,290330652147,1013504710004,3538006716150,12350698916311
%N A251221 Number of (n+1) X (1+1) 0..1 arrays with no 2 X 2 subblock having the minimum of its diagonal elements greater than the absolute difference of its antidiagonal elements.
%C A251221 Column 1 of A251228.
%H A251221 R. H. Hardin, <a href="/A251221/b251221.txt">Table of n, a(n) for n = 1..210</a>
%F A251221 Empirical: a(n) = 3*a(n-1) + 2*a(n-2) - a(n-3).
%F A251221 Empirical g.f.: x*(14 + 7*x - 4*x^2) / (1 - 3*x - 2*x^2 + x^3). - _Colin Barker_, Feb 25 2018
%e A251221 Some solutions for n=4:
%e A251221 ..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..0....1..0
%e A251221 ..1..0....0..1....1..1....0..0....0..1....1..0....0..0....0..1....0..0....0..0
%e A251221 ..1..0....0..0....0..0....0..1....1..1....1..0....0..0....0..1....1..0....0..1
%e A251221 ..0..0....0..0....0..0....0..1....0..1....1..1....0..1....0..0....1..1....1..0
%e A251221 ..1..0....0..0....1..0....1..1....0..0....0..0....1..1....0..0....1..0....1..0
%Y A251221 Cf. A251228.
%K A251221 nonn
%O A251221 1,1
%A A251221 _R. H. Hardin_, Nov 30 2014