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A228501 Number of n X 3 binary arrays with top left value 1 and no two ones adjacent horizontally, vertically, diagonally or antidiagonally. 1
2, 3, 12, 29, 88, 239, 684, 1909, 5392, 15143, 42644, 119933, 337512, 949535, 2671740, 7517061, 21150272, 59508247, 167433188, 471090573, 1325464216, 3729333775, 10492879052, 29522830997, 83065631600, 233713998087, 657579228980 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + 3*a(n-2) - 2*a(n-3).
Empirical g.f.: x*(2 - x) / (1 - 2*x - 3*x^2 + 2*x^3). - Colin Barker, Sep 11 2018
EXAMPLE
Some solutions for n=4:
..1..0..1....1..0..0....1..0..1....1..0..0....1..0..0....1..0..1....1..0..0
..0..0..0....0..0..1....0..0..0....0..0..0....0..0..0....0..0..0....0..0..1
..0..0..1....0..0..0....0..0..1....1..0..1....0..0..0....0..1..0....0..0..0
..0..0..0....1..0..0....1..0..0....0..0..0....0..0..1....0..0..0....0..0..0
CROSSREFS
Column 3 of A228506.
Sequence in context: A215602 A325628 A359221 * A089414 A260631 A195913
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 23 2013
STATUS
approved

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Last modified June 15 13:08 EDT 2024. Contains 373407 sequences. (Running on oeis4.)