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A224545 Number of (n+1) X 4 0..1 matrices with each 2 X 2 subblock idempotent. 1
28, 52, 78, 125, 193, 302, 472, 743, 1175, 1868, 2982, 4777, 7673, 12350, 19908, 32127, 51887, 83848, 135550, 219193, 354517, 573462, 927708, 1500875, 2428263, 3928792, 6356682, 10285073, 16641325, 26925938, 43566772, 70492187, 114058403 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 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) for n>6.

Empirical g.f.: x*(28 - 60*x + 10*x^2 + 45*x^3 - 25*x^4 + x^5) / ((1 - x)^3*(1 - x - x^2)). - Colin Barker, Aug 30 2018

EXAMPLE

Some solutions for n=3:

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

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

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

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

CROSSREFS

Cf. A224550.

Sequence in context: A291855 A181792 A181793 * A216303 A261105 A043134

Adjacent sequences: A224542 A224543 A224544 * A224546 A224547 A224548

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 10 2013

STATUS

approved

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Last modified December 8 21:26 EST 2022. Contains 358698 sequences. (Running on oeis4.)