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A224667 Number of 5 X 5 0..n matrices with each 2 X 2 subblock idempotent. 1
196, 260, 332, 412, 500, 596, 700, 812, 932, 1060, 1196, 1340, 1492, 1652, 1820, 1996, 2180, 2372, 2572, 2780, 2996, 3220, 3452, 3692, 3940, 4196, 4460, 4732, 5012, 5300, 5596, 5900, 6212, 6532, 6860, 7196, 7540, 7892, 8252, 8620, 8996, 9380, 9772, 10172 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 4*n^2 + 52*n + 140.

Conjectures from Colin Barker, Sep 02 2018: (Start)

G.f.: 4*x*(49 - 82*x + 35*x^2) / (1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>3.

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

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

..0..1..0..0..1....0..0..1..0..1....0..0..1..0..1....2..0..1..0..1

CROSSREFS

Row 5 of A224665.

Sequence in context: A044870 A248021 A151713 * A118781 A119667 A023108

Adjacent sequences:  A224664 A224665 A224666 * A224668 A224669 A224670

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 14 2013

STATUS

approved

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)