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A221567 Number of 0..2 arrays of length n with each element differing from at least one neighbor by something other than 1 1
0, 5, 9, 25, 57, 141, 345, 853, 2097, 5149, 12633, 31013, 76161, 187053, 459369, 1128053, 2770065, 6802301, 16704249, 41020357, 100732833, 247366989, 607452297, 1491704341, 3663139761, 8995478557, 22089965337, 54245756261, 133209897153 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A221573

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 3*a(n-1) -2*a(n-2) +4*a(n-4).

Empirical g.f.: -x^2*(5-6*x+8*x^2) / ( -1+3*x-2*x^2+4*x^4 ). - R. J. Mathar, Jun 06 2013

EXAMPLE

Some solutions for n=6

..2....1....2....0....0....1....2....0....0....0....0....2....0....2....0....1

..0....1....2....0....0....1....0....2....2....0....0....0....0....2....0....1

..0....1....1....2....2....0....0....2....2....2....2....1....2....1....0....2

..0....0....1....2....0....0....0....0....0....0....2....1....2....1....2....2

..2....0....2....2....2....1....1....2....0....0....1....2....2....2....0....0

..0....0....2....2....2....1....1....2....2....2....1....0....0....0....0....2

CROSSREFS

Sequence in context: A127976 A147286 A137199 * A147512 A301960 A050359

Adjacent sequences:  A221564 A221565 A221566 * A221568 A221569 A221570

KEYWORD

nonn

AUTHOR

R. H. Hardin Jan 20 2013

STATUS

approved

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Last modified August 11 09:58 EDT 2022. Contains 356065 sequences. (Running on oeis4.)