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A196906
Number of n X 2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 3,1,2,0,4 for x=0,1,2,3,4.
2
2, 6, 13, 34, 81, 199, 487, 1190, 2910, 7115, 17398, 42539, 104013, 254325, 621854, 1520506, 3717817, 9090502, 22227349, 54348491, 132888475, 324928002, 794487306, 1942615215, 4749923434, 11614123295, 28397901945, 69436221265, 169779754602
OFFSET
1,1
COMMENTS
Every 0 is next to 0 3's, every 1 is next to 1 1's, every 2 is next to 2 2's, every 3 is next to 3 0's, every 4 is next to 4 4's.
Column 2 of A196912.
LINKS
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-2) + 3*a(n-3) + 2*a(n-4) - a(n-6).
Empirical g.f.: x*(2 + 4*x + 3*x^2 + 3*x^3 - x^4 - x^5) / (1 - x - 2*x^2 - 3*x^3 - 2*x^4 + x^6). - Colin Barker, Mar 01 2018
EXAMPLE
Some solutions for n=4:
..1..1....1..1....0..1....1..1....2..2....1..1....0..0....1..1....1..1....2..2
..0..0....0..0....0..1....0..0....2..2....0..0....2..2....0..0....2..2....2..2
..1..0....0..0....0..0....0..1....0..1....1..1....2..2....2..2....2..2....0..0
..1..0....0..0....0..0....0..1....0..1....0..0....0..0....2..2....0..0....1..1
CROSSREFS
Cf. A196912.
Sequence in context: A098407 A151390 A116426 * A162057 A026550 A319751
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 07 2011
STATUS
approved