A256814 Number of length n+6 0..1 arrays with at most two downsteps in every 6 consecutive neighbor pairs.

120, 229, 442, 856, 1656, 3204, 6192, 11955, 23088, 44617, 86226, 166620, 321960, 622104, 1202016, 2322567, 4487848, 8671757, 16756074, 32377024, 62560664, 120883084, 233577104, 451331323, 872088416, 1685098737, 3256043394

Offset: 1

Author

R. H. Hardin, Apr 10 2015

Keywords

• nonn

Comments

Column 6 of A256816.

Examples

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

Links

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

Crossrefs

Cf. A256816.

Formula

Empirical: a(n) = 2*a(n-1) -a(n-2) +2*a(n-3) -a(n-4) +3*a(n-6) -2*a(n-7) -6*a(n-9) +4*a(n-10).

Empirical g.f.: x*(120 - 11*x + 104*x^2 - 39*x^3 + 48*x^4 + 93*x^5 - 190*x^6 - 128*x^7 - 250*x^8 + 252*x^9) / ((1 - x)*(1 - x - 2*x^3 - x^4 - x^5 - 4*x^6 - 2*x^7 - 2*x^8 + 4*x^9)). - Colin Barker, Jan 24 2018