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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. 3

%I

%S 14,49,171,597,2084,7275,25396,88654,309479,1080349,3771351,13165272,

%T 45958169,160433700,560052166,1955065729,6824867819,23824682749,

%U 83168718156,290330652147,1013504710004,3538006716150,12350698916311

%N 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 Column 1 of A251228.

%H R. H. Hardin, <a href="/A251221/b251221.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 3*a(n-1) + 2*a(n-2) - a(n-3).

%F Empirical g.f.: x*(14 + 7*x - 4*x^2) / (1 - 3*x - 2*x^2 + x^3). - _Colin Barker_, Feb 25 2018

%e Some solutions for n=4:

%e ..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..0....1..0

%e ..1..0....0..1....1..1....0..0....0..1....1..0....0..0....0..1....0..0....0..0

%e ..1..0....0..0....0..0....0..1....1..1....1..0....0..0....0..1....1..0....0..1

%e ..0..0....0..0....0..0....0..1....0..1....1..1....0..1....0..0....1..1....1..0

%e ..1..0....0..0....1..0....1..1....0..0....0..0....1..1....0..0....1..0....1..0

%Y Cf. A251228.

%K nonn

%O 1,1

%A _R. H. Hardin_, Nov 30 2014

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Last modified January 28 19:15 EST 2023. Contains 359905 sequences. (Running on oeis4.)