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A208009 Number of n X 4 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 1 and 0 1 1 vertically. 1
9, 81, 261, 841, 1943, 4489, 8643, 16641, 28509, 48841, 77129, 121801, 181131, 269361, 382503, 543169, 743633, 1018081, 1353069, 1798281, 2331999, 3024121, 3841451, 4879681, 6090213, 7601049, 9343473, 11485321, 13932179, 16900321 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Column 4 of A208013.
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + 4*a(n-2) - 10*a(n-3) - 5*a(n-4) + 20*a(n-5) - 20*a(n-7) + 5*a(n-8) + 10*a(n-9) - 4*a(n-10) - 2*a(n-11) + a(n-12).
Empirical g.f.: x*(9 + 63*x + 63*x^2 + 85*x^3 + 72*x^4 + 74*x^5 - 12*x^6 - 6*x^7 + 15*x^8 - x^9 - 3*x^10 + x^11) / ((1 - x)^7*(1 + x)^5). - Colin Barker, Jun 26 2018
EXAMPLE
Some solutions for n=4:
..1..0..0..1....1..1..0..0....0..1..0..0....1..0..0..1....0..1..0..0
..1..0..0..1....0..0..1..0....0..1..0..0....0..1..1..0....1..1..1..0
..1..0..0..1....0..1..0..0....0..1..0..0....1..0..0..1....0..1..0..0
..1..0..0..1....0..0..1..0....0..1..0..0....0..1..1..0....0..0..1..0
CROSSREFS
Cf. A208013.
Sequence in context: A223189 A207781 A207165 * A207909 A208421 A209646
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 22 2012
STATUS
approved

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Last modified July 14 18:31 EDT 2024. Contains 374322 sequences. (Running on oeis4.)