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URL: https://oeis.org/A251320

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A251320
Number of (n+1) X (2+1) 0..1 arrays with every 2 X 2 subblock having one or two 1s.
1
28, 116, 474, 1982, 8218, 34288, 142600, 594236, 2473510, 10302766, 42897286, 178649320, 743905252, 3097889852, 12900178658, 53720031766, 223702349874, 931554901848, 3879218692624, 16154045069844, 67269408740158
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) + 8*a(n-2) - 13*a(n-3) - a(n-4) + 2*a(n-5).
Empirical g.f.: 2*x*(14 + 16*x - 49*x^2 - 2*x^3 + 8*x^4) / ((1 + 2*x - x^2)*(1 - 5*x + 3*x^2 + 2*x^3)). - Colin Barker, Nov 28 2018
EXAMPLE
Some solutions for n=4:
..1..1..1....1..0..1....0..0..1....1..0..1....0..0..1....1..0..0....0..1..0
..0..0..0....0..0..1....1..0..0....1..0..1....1..0..1....1..0..1....0..1..0
..0..1..1....0..1..0....0..1..0....1..0..0....0..1..0....0..0..1....1..0..1
..1..0..0....0..0..1....0..0..1....0..0..1....0..1..0....1..0..1....1..0..1
..1..0..1....1..0..1....1..0..1....1..0..0....1..0..0....1..0..0....0..0..0
CROSSREFS
Column 2 of A251326.
Sequence in context: A042534 A042536 A042538 * A233372 A220755 A244079
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 01 2014
STATUS
approved