

A239333


Number of n X 1 0..3 arrays with no element equal to one plus the sum of elements to its left or three plus the sum of elements above it, modulo 4.


9



2, 5, 12, 28, 66, 156, 368, 868, 2048, 4832, 11400, 26896, 63456, 149712, 353216, 833344, 1966112, 4638656, 10944000, 25820224, 60917760, 143723520, 339087488, 800010496, 1887468032, 4453111040, 10506243072, 24787422208, 58481066496
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OFFSET

1,1


COMMENTS



LINKS



FORMULA

Empirical: a(n) = 2*a(n1) +2*a(n3).
Empirical g.f.: (2 + x + 2*x^2) / (1  2*x  2*x^3).  Colin Barker, Feb 18 2018


EXAMPLE

Some solutions for n=5:
..0....2....2....2....0....0....0....0....2....2....2....2....2....0....2....2
..2....0....2....0....2....0....2....0....0....0....0....2....2....2....0....3
..2....2....2....3....2....2....3....0....2....2....3....0....0....0....3....2
..0....0....0....2....2....2....2....0....2....2....3....0....2....0....2....3
..2....2....2....0....2....0....0....0....3....0....2....2....3....2....3....2


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



