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A229750 Number of defective 4-colorings of an n X 3 0..3 array connected horizontally, vertically, diagonally and antidiagonally with exactly two mistakes, and colors introduced in row-major 0..3 order. 1
1, 60, 598, 2347, 6809, 17404, 41872, 97565, 223075, 503650, 1126490, 2500555, 5515189, 12096536, 26401012, 57368137, 124167191, 267790942, 575680798, 1233926231, 2637709321, 5624580148, 11966370008, 25404922357, 53829723019 (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) = 9*a(n-1) - 33*a(n-2) + 63*a(n-3) - 66*a(n-4) + 36*a(n-5) - 8*a(n-6) for n>8.

Conjectures from Colin Barker, Sep 21 2018: (Start)

G.f.: x*(1 + 51*x + 91*x^2 - 1118*x^3 + 1706*x^4 - 176*x^5 - 612*x^6 - 64*x^7) / ((1 - x)^3*(1 - 2*x)^3).

a(n) = (2*(1732+117*2^n) + (-4084+279*2^n)*n + (484+9*2^n)*n^2) / 8 for n>2.

(End)

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 3 of A229755.

Sequence in context: A316458 A184191 A101384 * A223338 A081384 A283786

Adjacent sequences:  A229747 A229748 A229749 * A229751 A229752 A229753

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 28 2013

STATUS

approved

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Last modified October 28 19:06 EDT 2020. Contains 338064 sequences. (Running on oeis4.)