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%I #4 Apr 10 2013 10:50:11
%S 50,94,180,286,540,992,1668,2852,4870,8086,13318,21860,35536,57364,
%T 92210,147516,234942,372868,589854,930262,1463134,2295546,3593192,
%U 5612308,8748560,13611938,21141762,32782810
%N Number of (n+2)X(n+2) 0..1 matrices with each 3X3 subblock idempotent
%C Diagonal of A224559
%F Empirical: a(n) = 6*a(n-1) -15*a(n-2) +23*a(n-3) -30*a(n-4) +36*a(n-5) -34*a(n-6) +27*a(n-7) -21*a(n-8) +13*a(n-9) -6*a(n-10) +3*a(n-11) -a(n-12) for n>14
%e Some solutions for n=3
%e ..1..0..0..0..0....1..1..0..0..0....1..0..0..0..0....1..0..0..0..0
%e ..1..0..0..0..0....0..0..0..0..0....0..0..0..0..1....1..0..0..0..1
%e ..1..0..0..0..0....0..0..0..0..1....0..0..0..0..1....0..0..0..0..1
%e ..1..0..0..0..0....0..0..0..0..1....0..0..0..0..1....0..0..0..0..1
%e ..1..0..0..0..0....0..0..0..0..1....0..0..0..0..1....0..0..0..0..1
%K nonn
%O 1,1
%A _R. H. Hardin_ Apr 10 2013