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A229666 Number of defective 4-colorings of an n X 2 0..3 array connected horizontally, antidiagonally and vertically with exactly two mistakes, and colors introduced in row-major 0..3 order. 1
0, 4, 61, 652, 5048, 33152, 197248, 1098752, 5838848, 29949952, 149454848, 729546752, 3497525248, 16517169152, 77015810048, 355207217152, 1622826549248, 7352984010752, 33073395662848, 147798414589952, 656648959950848 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = 12*a(n-1) - 48*a(n-2) + 64*a(n-3) for n>6.

Conjectures from Colin Barker, Sep 20 2018: (Start)

G.f.: x^2*(4 + 13*x + 112*x^2 - 104*x^3 - 32*x^4) / (1 - 4*x)^3.

a(n) = 2^(2*n-7) * (106 - 145*n + 50*n^2) for n>3.

(End)

EXAMPLE

Some solutions for n=3:

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

..0..2....2..2....1..0....2..3....2..1....0..1....2..2....1..2....1..2....1..2

..1..1....0..0....1..2....2..2....1..3....2..3....1..2....0..0....0..0....1..3

CROSSREFS

Column 2 of A229672.

Sequence in context: A131014 A118005 A132064 * A252973 A262654 A218472

Adjacent sequences:  A229663 A229664 A229665 * A229667 A229668 A229669

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 27 2013

STATUS

approved

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Last modified September 21 09:06 EDT 2021. Contains 347597 sequences. (Running on oeis4.)