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A213691 Half the number of (n+1)X(n+1) symmetric 0..2 arrays with no 2X2 subblock summing to 4.

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%I A213691 #5 Jun 02 2025 08:03:17
%S A213691 11,192,7827,750261,168382284,88681187619,109492322533385,
%T A213691 317058871268862262,2152886481426876004067,34281579489759899253123057,
%U A213691 1280103594445094955653155909620,112093309434087933528612875492895053
%N A213691 Half the number of (n+1)X(n+1) symmetric 0..2 arrays with no 2X2 subblock summing to 4.
%C A213691 Column 2 of A213697
%e A213691 Some solutions for n=4
%e A213691 ..0..0..2..0..0....0..0..2..1..0....2..2..2..1..1....0..2..0..0..1
%e A213691 ..0..0..1..2..0....0..1..2..0..2....2..0..2..2..1....2..1..2..0..1
%e A213691 ..2..1..1..2..2....2..2..0..0..0....2..2..1..0..2....0..2..2..2..2
%e A213691 ..0..2..2..0..1....1..0..0..2..0....1..2..0..2..1....0..0..2..0..1
%e A213691 ..0..0..2..1..1....0..2..0..0..0....1..1..2..1..2....1..1..2..1..1
%K A213691 nonn
%O A213691 1,1
%A A213691 _R. H. Hardin_ Jun 18 2012

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