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A281471
Number of 3 X n 0..1 arrays with no element equal to more than two of its horizontal, diagonal or antidiagonal neighbors and with new values introduced in order 0 sequentially upwards.
1
4, 25, 24, 39, 57, 87, 145, 241, 397, 669, 1133, 1909, 3229, 5477, 9277, 15717, 26653, 45189, 76605, 129893, 220253, 373445, 633213, 1073701, 1820573, 3086981, 5234365, 8875493, 15049437, 25518149, 43269117, 73367973, 124404253, 210942469
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) - a(n-2) + 2*a(n-3) - 2*a(n-4) for n>8.
Empirical g.f.: x*(4 + 17*x - 22*x^2 + 8*x^3 - 39*x^4 + 14*x^5 - 2*x^6 + 2*x^7) / ((1 - x)*(1 - x - 2*x^3)). - Colin Barker, Feb 19 2019
EXAMPLE
Some solutions for n=4:
..0..1..0..1. .0..0..1..0. .0..1..0..1. .0..1..0..1. .0..1..1..0
..0..1..0..0. .1..0..1..0. .1..1..0..1. .0..1..0..0. .0..0..1..0
..0..1..1..0. .0..0..1..1. .1..0..0..1. .1..0..1..1. .1..0..1..1
CROSSREFS
Row 3 of A281469.
Sequence in context: A111446 A114390 A114392 * A107734 A302624 A238515
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 22 2017
STATUS
approved