A229679 Number of defective 3-colorings of an n X 2 0..2 array connected diagonally and antidiagonally with exactly two mistakes, and colors introduced in row-major 0..2 order.

0, 2, 36, 360, 2688, 17280, 101376, 559104, 2949120, 15040512, 74711040, 363331584, 1736441856, 8178892800, 38050725888, 175154135040, 798863917056, 3614214979584, 16234976378880, 72464688218112, 321607151124480

Offset

1,2

Comments

Column 2 of A229685.

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>5.

Empirical g.f.: 2*x^2 - 12*x^3*(3-6*x+8*x^2) / (4*x-1)^3. - R. J. Mathar, Sep 29 2013

Empirical: a(n) = 3*2^(2*n-5)*(3 - 5*n + 2*n^2) for n>2. - Colin Barker, Jun 13 2017

Example

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

Crossrefs

Sequence in context: A273325 A035603 A126735 * A119582 A157055 A057407

Adjacent sequences: A229676 A229677 A229678 * A229680 A229681 A229682

Keyword

nonn

Author

R. H. Hardin, Sep 27 2013

Status

approved