A229600 Number of defective 3-colorings of an n X 2 0..2 array connected horizontally and vertically with exactly two mistakes, and colors introduced in row-major 0..2 order.

0, 6, 39, 202, 925, 3924, 15795, 61182, 230121, 845640, 3049407, 10825650, 37929141, 131403708, 450839115, 1533738726, 5178892545, 17371743408, 57926537559, 192131864730, 634207340493, 2084322230820, 6822862231779, 22252658047182

Offset

1,2

Comments

Column 2 of A229606.

Links

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

Formula

Empirical: a(n) = 9*a(n-1) - 27*a(n-2) + 27*a(n-3) for n>5.

Conjectures from Colin Barker, Mar 16 2018: (Start)

G.f.: x^2*(6 - 15*x + 13*x^2 - 2*x^3) / (1 - 3*x)^3.

a(n) = 3^(n-5) * (31*n+32*n^2-30) for n>2.

(End)

Example

Some solutions for n=3:
  0 1   0 1   0 1   0 0   0 1   0 1   0 1   0 1   0 1   0 1
  1 2   2 0   0 1   0 1   1 2   2 1   2 2   1 1   2 2   2 2
  1 2   2 0   2 0   1 2   2 2   2 0   1 1   2 0   0 2   2 0

Crossrefs

Cf. A229606.

Sequence in context: A159571 A007793 A297579 * A339205 A258342 A037592

Adjacent sequences: A229597 A229598 A229599 * A229601 A229602 A229603

Keyword

nonn

Author

R. H. Hardin, Sep 26 2013

Status

approved