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A240389
Number of n X 2 0..3 arrays with no element equal to zero plus the sum of elements to its left or one plus the sum of elements above it or two plus the sum of the elements diagonally to its northwest, modulo 4.
1
1, 5, 12, 50, 120, 493, 1184, 4863, 11684, 47994, 115320, 473699, 1138208, 4675397, 11234076, 46145994, 110879896, 455459165, 1094380256, 4495364247, 10801490596, 44369070466, 106610292568, 437921001875, 1052239446112, 4322263276333
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 12*a(n-2) - 24*a(n-4) + 31*a(n-6) - 16*a(n-8).
Empirical g.f.: x*(1 + 5*x - 10*x^3 + 13*x^5 + x^6 - 8*x^7) / (1 - 12*x^2 + 24*x^4 - 31*x^6 + 16*x^8). - Colin Barker, Oct 27 2018
EXAMPLE
Some solutions for n=4:
..3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0
..3..0....1..2....3..2....1..2....3..0....1..0....1..3....1..2....3..2....3..2
..1..0....3..0....1..2....3..2....1..2....3..0....3..2....3..0....1..0....1..0
..3..2....1..0....1..0....3..2....3..1....1..2....1..3....3..0....3..2....1..2
CROSSREFS
Column 2 of A240394.
Sequence in context: A009425 A009416 A332477 * A135769 A074024 A054661
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 04 2014
STATUS
approved