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A203916
Number of (n+2) X 3 0..1 arrays with every 3 X 3 subblock having equal diagonal elements or equal antidiagonal elements, and new values 0..1 introduced in row major order.
1
112, 392, 1400, 5000, 17800, 63368, 225704, 803912, 2863144, 10197128, 36317672, 129347528, 460677928, 1640728328, 5843540840, 20812080200, 74123322280, 263994125192, 940229020136, 3348675314888, 11926483984936, 42476802576392
OFFSET
1,1
COMMENTS
Column 1 of A203923.
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) +6*a(n-3) +4*a(n-4).
Empirical g.f.: 8*x*(14 + 7*x + 28*x^2 + 16*x^3) / ((1 + 2*x^2)*(1 - 3*x - 2*x^2)). - Colin Barker, Jun 05 2018
EXAMPLE
Some solutions for n=3:
..0..0..0....0..1..1....0..0..1....0..0..0....0..1..0....0..1..0....0..0..1
..1..0..0....1..0..1....1..0..1....1..0..0....0..0..0....0..0..0....1..1..1
..0..1..1....0..1..0....0..1..0....1..1..0....0..0..0....1..0..0....1..1..1
..1..1..1....1..0..0....1..0..1....0..1..1....0..0..1....0..1..0....1..1..1
..1..1..1....0..0..1....1..0..0....1..0..1....0..0..0....0..0..1....1..1..1
CROSSREFS
Cf. A203923.
Sequence in context: A235319 A203923 A235312 * A234681 A234674 A217992
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 07 2012
STATUS
approved