login
A232331
Number of nX4 0..2 arrays with every 0 next to a 1 and every 1 next to a 2 horizontally or antidiagonally, with no adjacent elements equal
1
6, 32, 154, 734, 3472, 16338, 76630, 358656, 1676330, 7828014, 36533360, 170436130, 794923238, 3706958560, 17284778298, 80589690622, 375729468240, 1751693001458, 8166429157878, 38071572583616, 177486683779786, 827424427937102
OFFSET
1,1
COMMENTS
Column 4 of A232335
LINKS
FORMULA
Empirical: a(n) = 7*a(n-1) -9*a(n-2) -8*a(n-3) -4*a(n-4).
Empirical: G.f.: -2*x*(-3+5*x+8*x^2+4*x^3) / ( 1-7*x+9*x^2+8*x^3+4*x^4 ). - R. J. Mathar, Nov 24 2013
EXAMPLE
Some solutions for n=7
..0..1..2..1....2..1..2..1....0..1..0..2....2..1..2..1....2..1..0..2
..2..1..0..2....0..1..0..2....2..1..0..2....0..1..2..1....2..1..0..1
..2..1..0..2....0..1..0..1....0..2..1..0....0..1..2..1....2..1..2..1
..2..1..0..2....2..1..2..1....1..0..1..0....0..1..0..2....0..1..0..2
..0..1..0..2....0..1..0..2....1..2..1..2....0..2..0..2....0..2..1..2
..2..1..0..2....0..2..1..0....1..2..1..0....0..1..0..1....1..0..1..0
..0..2..1..0....1..2..1..0....1..0..2..1....2..1..2..1....2..0..2..1
CROSSREFS
Sequence in context: A243026 A242542 A046725 * A231992 A292044 A006668
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 22 2013
STATUS
approved