A245866 Number of length n+2 0..5 arrays with some pair in every consecutive three terms totalling exactly 5.

90, 318, 960, 3102, 9726, 30900, 97602, 309078, 977664, 3094038, 9789654, 30977796, 98020170, 310161870, 981426624, 3105480558, 9826505742, 31093507092, 98387556594, 311322635814, 985101990912, 3117106968486, 9863299264806

Offset: 1

Author

R. H. Hardin, Aug 04 2014

Keywords

• nonn

Examples

			Some solutions for n=7:
  1   5   0   3   5   3   2   3   0   4   3   4   1   0   1   3
  5   4   3   1   2   0   2   4   1   0   2   1   4   2   0   0
  0   1   2   4   3   2   3   1   4   5   0   5   2   3   5   5
  2   0   3   5   3   5   4   5   0   0   3   0   1   1   0   0
  3   4   2   0   2   0   1   0   1   5   2   4   3   2   1   2
  2   5   3   5   1   5   4   0   4   3   4   1   2   3   4   5
  0   0   4   0   4   4   4   5   1   2   1   4   4   0   3   0
  5   4   1   3   1   0   1   2   0   0   4   1   3   5   1   4
  2   5   2   2   3   1   5   3   4   3   5   3   1   5   2   1
		

Links

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

Crossrefs

Column 5 of A245869.

Formula

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

Empirical g.f.: 6*x*(15 + 23*x - 6*x^2) / (1 - 2*x - 4*x^2 + x^3). - Colin Barker, Nov 04 2018