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A278095
Number of n X 2 0..3 arrays with every element plus 1 mod 4 equal to some element at offset (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero.
1
0, 2, 10, 58, 334, 1910, 10910, 62314, 355898, 2032630, 11608866, 66301138, 378662314, 2162634690, 12351344662, 70541601526, 402880631914, 2300951495750, 13141306298158, 75053268849534, 428647886076278, 2448114693124250
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) - a(n-2) - 3*a(n-3) - 3*a(n-4) - 6*a(n-5) + 2*a(n-7).
Empirical g.f.: 2*x^2*(1 - x + x^3) / (1 - 6*x + x^2 + 3*x^3 + 3*x^4 + 6*x^5 - 2*x^7). - Colin Barker, Feb 07 2019
EXAMPLE
Some solutions for n=4:
..0..3. .0..3. .0..1. .0..1. .0..3. .0..1. .0..3. .0..1. .0..3. .0..3
..1..2. .1..2. .3..2. .3..2. .1..2. .1..2. .1..0. .3..2. .1..2. .1..0
..1..1. .2..1. .3..0. .2..3. .0..1. .0..3. .2..3. .0..3. .0..3. .2..3
..0..0. .3..0. .2..1. .1..0. .0..0. .3..2. .1..2. .1..2. .2..1. .2..1
CROSSREFS
Column 2 of A278099.
Sequence in context: A371770 A369487 A248403 * A075870 A074608 A086871
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 12 2016
STATUS
approved