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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. 1
4, 16, 62, 240, 932, 3620, 14056, 54576, 211912, 822832, 3194960, 12405648, 48169664, 187037120, 726243040, 2819915904, 10949400256, 42515227456, 165081604736, 640992365568, 2488897617536, 9664095367424, 37524540428032 (list; graph; refs; listen; history; text; internal format)
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

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

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

CROSSREFS

Column 2 of A227442.

Sequence in context: A195339 A172025 A171278 * A206839 A244827 A169760

Adjacent sequences:  A227435 A227436 A227437 * A227439 A227440 A227441

KEYWORD

nonn

AUTHOR

R. H. Hardin Jul 11 2013

STATUS

approved

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Last modified September 29 02:55 EDT 2022. Contains 357082 sequences. (Running on oeis4.)