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A224544 Number of (n+1) X 3 0..1 matrices with each 2 X 2 subblock idempotent. 1
16, 32, 52, 86, 137, 218, 345, 547, 869, 1385, 2214, 3549, 5702, 9178, 14794, 23872, 38551, 62292, 100695, 162821, 263331, 425947, 689052, 1114751, 1803532, 2917988, 4721200, 7638842, 12359669, 19998110, 32357349, 52354999, 84711857, 137066333 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A224550.

LINKS

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

FORMULA

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

Empirical g.f.: x*(16 - 32*x + 4*x^2 + 22*x^3 - 11*x^4) / ((1 - x)^3*(1 - x - x^2)). - Colin Barker, Aug 30 2018

EXAMPLE

Some solutions for n=3:

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

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

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

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

CROSSREFS

Cf. A224550.

Sequence in context: A082294 A048946 A260050 * A255994 A204645 A236323

Adjacent sequences:  A224541 A224542 A224543 * A224545 A224546 A224547

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 10 2013

STATUS

approved

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Last modified August 9 12:53 EDT 2022. Contains 356026 sequences. (Running on oeis4.)