A229397 Number of n X 3 0..2 arrays with top left element 0, horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and antidiagonal differences never 0.

4, 13, 44, 153, 536, 1881, 6604, 23189, 81428, 285937, 1004080, 3525873, 12381268, 43477405, 152672956, 536118281, 1882604616, 6610854857, 23214328476, 81518208805, 286255033124, 1005198043361, 3529800316000, 12395060210401

Offset

1,1

Links

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

Formula

Empirical: a(n) = 5*a(n-1) - 6*a(n-2) + 3*a(n-3) - a(n-4).

Empirical g.f.: x*(4 - 7*x + 3*x^2 - x^3) / ((1 - x)*(1 - 4*x + 2*x^2 - x^3)). - Colin Barker, Sep 14 2018

Example

Some solutions for n=4:
  0 0 0   0 0 2   0 2 1   0 2 2   0 2 1   0 0 2   0 0 0
  1 1 0   1 0 0   1 0 2   1 0 0   1 0 2   1 0 0   1 1 0
  2 2 1   2 1 1   2 1 0   2 1 1   1 1 0   1 1 0   2 1 0
  0 2 2   2 2 2   2 2 1   2 2 1   2 2 1   2 1 0   2 1 1

Crossrefs

Column 3 of A229402.

Sequence in context: A149427 A290907 A252933 * A283110 A149428 A149429

Adjacent sequences: A229394 A229395 A229396 * A229398 A229399 A229400

Keyword

nonn

Author

R. H. Hardin, Sep 22 2013

Status

approved