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%I #10 Sep 03 2018 15:23:51
%S 2052,1623,2471,3506,4257,5737,8117,12306,18187,26561,38040,55162,
%T 80519,118413,173641,254339,371847,544345,797402,1169025,1713358,
%U 2510861,3678903,5391040,7900541,11579142,16970092,24870656,36448737,53417530
%N Number of (n+3) X 4 0..2 matrices with each 4 X 4 subblock idempotent.
%H R. H. Hardin, <a href="/A224721/b224721.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-4) - 2*a(n-5) + 2*a(n-6) - 2*a(n-7) + a(n-8) for n>11.
%F Empirical g.f.: x*(2052 - 4533*x + 3758*x^2 - 1090*x^3 - 2523*x^4 + 3494*x^5 - 3158*x^6 + 3203*x^7 - 1110*x^8 - 115*x^9 - 4*x^10) / ((1 - x)^2*(1 + x)*(1 - x + x^2)*(1 - x - x^3)). - _Colin Barker_, Sep 03 2018
%e Some solutions for n=2:
%e 1 1 0 2 1 1 2 0 1 2 2 0 0 0 0 0 1 0 0 0
%e 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2
%e 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
%e 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 1 1
%e 0 1 1 0 0 0 0 0 0 2 0 1 1 2 2 1 0 0 0 0
%Y Column 1 of A224728.
%K nonn
%O 1,1
%A _R. H. Hardin_, Apr 16 2013
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