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A181255 Number of (n+2) X 3 binary matrices with every 3 X 3 block having exactly four 1's. 1
126, 336, 906, 2484, 7218, 21024, 61398, 182520, 542754, 1614492, 4829706, 14448456, 43225326, 129555936, 388309626, 1163860164, 3490511778, 10468335024, 31395421638, 94176681480, 282501311634, 847417788972, 2542167220986 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A181262.

LINKS

R. H. Hardin, Table of n, a(n) for n=1..200

FORMULA

Empirical: a(n) = 3*a(n-1) + 12*a(n-3) - 36*a(n-4) - 27*a(n-6) + 81*a(n-7).

Empirical g.f.: 6*x*(21 - 7*x - 17*x^2 - 291*x^3 + 45*x^4 + 99*x^5 + 756*x^6) / ((1 - 3*x)*(1 - 3*x^3)*(1 - 9*x^3)). - Colin Barker, Mar 26 2018

EXAMPLE

Some solutions for 4X3:

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

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

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

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

CROSSREFS

Cf. A181262.

Sequence in context: A254465 A063334 A181262 * A322542 A323759 A102805

Adjacent sequences:  A181252 A181253 A181254 * A181256 A181257 A181258

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 10 2010

STATUS

approved

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Last modified June 24 17:50 EDT 2019. Contains 324330 sequences. (Running on oeis4.)