A227438 - OEIS

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A227438

Number of n X 2 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X 3 binary array having two adjacent 1's and two adjacent 0's.

4, 16, 62, 240, 932, 3620, 14056, 54576, 211912, 822832, 3194960, 12405648, 48169664, 187037120, 726243040, 2819915904, 10949400256, 42515227456, 165081604736, 640992365568, 2488897617536, 9664095367424, 37524540428032

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OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 4*a(n-1) - 2*a(n-2) + 6*a(n-3).

Empirical g.f.: 2*x*(2 + 3*x^2) / (1 - 4*x + 2*x^2 - 6*x^3). - Colin Barker, Sep 08 2018

EXAMPLE

Some solutions for n=4:

..1..0....1..0....1..0....0..0....1..0....1..1....1..1....0..1....0..0....1..1

..0..1....1..0....1..0....0..0....1..0....0..0....0..1....1..0....1..0....0..0