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A224666 Number of 4 X 4 0..n matrices with each 2 X 2 subblock idempotent. 1
78, 108, 142, 180, 222, 268, 318, 372, 430, 492, 558, 628, 702, 780, 862, 948, 1038, 1132, 1230, 1332, 1438, 1548, 1662, 1780, 1902, 2028, 2158, 2292, 2430, 2572, 2718, 2868, 3022, 3180, 3342, 3508, 3678, 3852, 4030, 4212, 4398, 4588, 4782, 4980, 5182 (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) = 2*n^2 + 24*n + 52.

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

G.f.: 2*x*(39 - 63*x + 26*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:

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

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

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

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

CROSSREFS

Row 4 of A224665.

Sequence in context: A025387 A025378 A157355 * A161596 A275218 A260364

Adjacent sequences:  A224663 A224664 A224665 * A224667 A224668 A224669

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 14 2013

STATUS

approved

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Last modified April 11 06:40 EDT 2021. Contains 342886 sequences. (Running on oeis4.)