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A229572 Number of defective 4-colorings of an n X 2 0..3 array connected horizontally, vertically, diagonally and antidiagonally with exactly one mistake, and colors introduced in row-major 0..3 order. 1
1, 6, 26, 80, 216, 544, 1312, 3072, 7040, 15872, 35328, 77824, 169984, 368640, 794624, 1703936, 3637248, 7733248, 16384000, 34603008, 72876032, 153092096, 320864256, 671088640, 1400897536, 2919235584, 6073352192, 12616466432, 26172456960 (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) = 4*a(n-1) - 4*a(n-2) for n>3.

Conjectures from Colin Barker, Sep 19 2018: (Start)

G.f.: x*(1 + 2*x + 6*x^2) / (1 - 2*x)^2.

a(n) = 2^(n-2) * (7*n-8) for n>1.

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Column 2 of A229578.

Sequence in context: A255870 A286188 A094162 * A316160 A224035 A172207

Adjacent sequences:  A229569 A229570 A229571 * A229573 A229574 A229575

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 26 2013

STATUS

approved

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Last modified November 21 09:14 EST 2019. Contains 329362 sequences. (Running on oeis4.)