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%I #8 Jun 05 2018 08:19:03
%S 784,10576,142192,1911952,25708528,345682576,4648124656,62499715984,
%T 840385055728,11300004020368,151942362599152,2043050737911184,
%U 27471313768440304,369385383417191056,4966837867034125552
%N Number of (n+1) X 3 0..3 arrays with every 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements.
%C Column 2 of A203796.
%H R. H. Hardin, <a href="/A203790/b203790.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 13*a(n-1) +6*a(n-2).
%F Empirical g.f.: 16*x*(49 + 24*x) / (1 - 13*x - 6*x^2). - _Colin Barker_, Jun 05 2018
%e Some solutions for n=4:
%e ..0..2..3....0..1..0....1..3..2....1..0..0....3..2..2....3..1..3....2..1..1
%e ..3..0..2....3..0..1....2..1..3....0..0..3....1..3..2....1..3..3....2..2..1
%e ..2..3..0....1..3..0....2..2..1....1..0..0....1..1..3....3..1..3....0..2..2
%e ..3..1..3....3..1..3....0..2..2....0..1..0....0..1..1....1..3..2....3..0..2
%e ..1..3..3....0..3..0....2..2..1....1..3..1....0..0..1....3..0..3....2..3..0
%Y Cf. A203796.
%K nonn
%O 1,1
%A _R. H. Hardin_, Jan 05 2012
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