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%I #11 Mar 09 2024 16:26:06
%S 4,8,14,26,46,86,158,302,574,1118,2174,4286,8446,16766,33278,66302,
%T 132094,263678,526334,1051646,2101246,4200446,8396798,16789502,
%U 33570814,67133438,134250494,268484606,536936446,1073840126,2147614718,4295163902
%N 1/4 the number of (n+1) X (n+1) binary arrays with all 2 X 2 subblock sums the same.
%H Andrew Howroyd, <a href="/A183977/b183977.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (3,0,-6,4).
%F From _Andrew Howroyd_, Mar 09 2024: Start)
%F a(n) = 3*a(n-1) - 6*a(n-3) + 4*a(n-4).
%F G.f.: 2*x*(2 - 2*x - 5*x^2 + 4*x^3)/((1 - x)*(1 - 2*x)*(1 - 2*x^2)). (End)
%e Some solutions for 5X5
%e ..1..0..1..0..1....0..1..0..1..0....1..1..1..1..1....0..1..1..0..1
%e ..1..0..1..0..1....1..0..1..0..1....0..1..0..1..0....1..0..0..1..0
%e ..0..1..0..1..0....1..0..1..0..1....1..1..1..1..1....0..1..1..0..1
%e ..1..0..1..0..1....1..0..1..0..1....1..0..1..0..1....1..0..0..1..0
%e ..0..1..0..1..0....1..0..1..0..1....1..1..1..1..1....0..1..1..0..1
%o (PARI) Vec(2*(2 - 2*x - 5*x^2 + 4*x^3)/((1 - x)*(1 - 2*x)*(1 - 2*x^2)) + O(x^32)) \\ _Andrew Howroyd_, Mar 09 2024
%Y Diagonal of A183986.
%K nonn,easy
%O 1,1
%A _R. H. Hardin_, Jan 08 2011
%E a(19) onwards from _Andrew Howroyd_, Mar 09 2024
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