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A224666
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Number of 4 X 4 0..n matrices with each 2 X 2 subblock idempotent.
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1
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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
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OFFSET
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1,1
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..210
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FORMULA
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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)
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EXAMPLE
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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
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CROSSREFS
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Row 4 of A224665.
Sequence in context: A025387 A025378 A157355 * A161596 A275218 A260364
Adjacent sequences: A224663 A224664 A224665 * A224667 A224668 A224669
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Apr 14 2013
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STATUS
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approved
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