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A240631
Number of n X 3 0..1 arrays with no element equal to exactly three horizontal or vertical neighbors, with new values 0..1 introduced in row major order.
1
4, 25, 129, 637, 3147, 15590, 77269, 382933, 1897681, 9404215, 46603960, 230952833, 1144520961, 5671842895, 28107656217, 139291647132, 690280357055, 3420786394205, 16952212872439, 84009197931223, 416320004365162
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) + 4*a(n-2) + 2*a(n-3) + 7*a(n-4) + 6*a(n-5) - a(n-6) - a(n-7) - a(n-8).
Empirical g.f.: x*(4 + 9*x + 13*x^2 + 13*x^3 + 5*x^4 - 3*x^5 - 2*x^6 - x^7) / (1 - 4*x - 4*x^2 - 2*x^3 - 7*x^4 - 6*x^5 + x^6 + x^7 + x^8). - Colin Barker, Oct 29 2018
EXAMPLE
Some solutions for n=4:
..0..1..0....0..1..1....0..1..1....0..1..0....0..0..1....0..0..0....0..1..1
..1..1..0....1..0..0....0..1..0....1..1..1....0..0..1....0..1..0....1..0..0
..1..0..1....0..1..1....0..1..0....0..1..1....1..1..0....1..1..1....0..0..1
..0..0..1....1..0..0....0..1..0....0..0..0....1..0..0....0..1..1....1..1..0
CROSSREFS
Column 3 of A240636.
Sequence in context: A240479 A317949 A263440 * A123660 A304842 A156701
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 09 2014
STATUS
approved