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A183629
Number of (n+1) X 7 0..2 arrays with every 2 X 2 subblock summing to 4.
1
2445, 2967, 4029, 6207, 10725, 20247, 40749, 86127, 190005, 437127, 1049469, 2628447, 6849285, 18479607, 51306189, 145657167, 420452565, 1228323687, 3618906909, 10724596287, 31909543845, 95200145367, 284543467629
OFFSET
1,1
COMMENTS
Column 6 of A183632.
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3).
Conjectures from Colin Barker, Mar 31 2018: (Start)
G.f.: 3*x*(815 - 3901*x + 4374*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)).
a(n) = 3*(644 + 21*2^(2+n) + 3^n).
(End)
EXAMPLE
Some solutions for 3 X 7:
1 1 0 1 1 0 1 2 0 1 1 2 1 1 0 2 1 2 0 1 1
1 1 2 1 1 2 1 1 1 2 0 1 0 2 1 1 0 1 1 2 0
1 1 0 1 1 0 1 2 0 1 1 2 1 1 0 2 1 2 0 1 1
CROSSREFS
Cf. A183632.
Sequence in context: A259000 A256898 A255077 * A274684 A232141 A251338
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 06 2011
STATUS
approved