A235232 Number of (n+1) X (1+1) 0..6 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 6, with no adjacent elements equal (constant-stress tilted 1 X 1 tilings).

120, 420, 1328, 4652, 14944, 52468, 170864, 601100, 1980544, 6979348, 23223440, 81953324, 274931488, 971325748, 3280518320, 11600884556, 39397352128, 139427487316, 475663660496, 1684432450412, 5768254899040, 20437259824756

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 23*a(n-2) - 63*a(n-3) - 153*a(n-4) + 333*a(n-5) + 249*a(n-6) - 81*a(n-7) - 54*a(n-8).

Empirical g.f.: 4*x*(30 + 15*x - 673*x^2 - 358*x^3 + 3816*x^4 + 2151*x^5 - 933*x^6 - 528*x^7) / ((1 - 3*x)*(1 + 3*x)*(1 - 3*x - 2*x^2)*(1 - 12*x^2 + 3*x^4)). - Colin Barker, Oct 17 2018

Example

Some solutions for n=4:
  2 0   2 1   2 4   3 0   1 3   4 1   3 6   4 1   5 0   2 5
  1 5   0 5   6 2   2 5   4 0   0 3   5 2   3 6   4 5   4 1
  3 1   1 0   3 5   6 3   1 3   3 0   0 3   5 2   6 1   0 3
  0 4   0 5   5 1   3 6   4 0   1 4   4 1   2 5   2 3   3 0
  2 0   3 2   4 6   4 1   0 2   5 2   3 6   5 2   5 0   1 4

Crossrefs

Column 1 of A235239.

Sequence in context: A307933 A235239 A337469 * A304284 A167562 A033697

Adjacent sequences: A235229 A235230 A235231 * A235233 A235234 A235235

Keyword

nonn

Author

R. H. Hardin, Jan 05 2014

Status

approved