A227747 Number of n X 2 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X 3 binary array having determinant equal to one.

4, 13, 40, 129, 409, 1300, 4137, 13152, 41825, 133009, 422964, 1345045, 4277288, 13601889, 43254441, 137550436, 437414545, 1390991616, 4423395649, 14066532769, 44732002468, 142249129309, 452356561000, 1438507633089, 4574498058553

Offset

1,1

Links

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

Formula

Empirical: a(n) = a(n-1) + 4*a(n-2) + 8*a(n-3) + 4*a(n-4) + a(n-5) - a(n-6).

Empirical g.f.: x*(4 + 9*x + 11*x^2 + 5*x^3 - x^5) / (1 - x - 4*x^2 - 8*x^3 - 4*x^4 - x^5 + x^6). - Colin Barker, Sep 09 2018

Example

Some solutions for n=4:
..1..1....0..0....1..0....0..0....1..1....0..0....1..0....0..0....1..0....1..1
..0..1....0..0....0..1....0..0....0..0....1..1....0..1....0..0....1..1....0..1
..1..0....0..0....1..0....1..1....0..0....0..0....1..0....0..0....0..0....0..0
..1..1....0..1....0..1....0..0....0..0....1..0....1..0....1..0....0..1....1..0

Crossrefs

Column 2 of A227751.

Sequence in context: A091141 A098183 A171556 * A094628 A379201 A034742

Adjacent sequences: A227744 A227745 A227746 * A227748 A227749 A227750

Keyword

nonn

Author

R. H. Hardin, Jul 25 2013

Status

approved