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

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