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A229472
Number of defective 4-colorings of an n X 1 0..3 array connected horizontally, antidiagonally and vertically with exactly one mistake, and colors introduced in row-major 0..3 order.
2
0, 1, 2, 6, 20, 70, 246, 854, 2920, 9846, 32810, 108262, 354300, 1151462, 3720094, 11957430, 38263760, 121965718, 387420498, 1226831558, 3874204900, 12203745414, 38354628422, 120294061846, 376572715320, 1176789735350, 3671583974266
OFFSET
1,3
COMMENTS
Column 1 of A229479.
LINKS
FORMULA
Empirical: a(n) = 8*a(n-1) - 22*a(n-2) + 24*a(n-3) - 9*a(n-4) for n>6.
Conjectures from Colin Barker, Mar 16 2018: (Start)
G.f.: x^2*(1 - 6*x + 12*x^2 - 8*x^3 + 3*x^4) / ((1 - x)^2*(1 - 3*x)^2).
a(n) = (27+3^n) * (n-1) / 54 for n>2.
(End)
EXAMPLE
All solutions for n=4:
0 0 0 0 0 0
0 1 1 1 1 0
1 0 1 2 1 1
0 0 2 2 0 2
CROSSREFS
Cf. A229479.
Sequence in context: A150124 A045631 A275046 * A135413 A193653 A147748
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 24 2013
STATUS
approved