A255991 Number of length n+7 0..1 arrays with at most one downstep in every 7 consecutive neighbor pairs.

93, 136, 207, 328, 530, 854, 1352, 2088, 3175, 4824, 7406, 11528, 18124, 28562, 44768, 69584, 107469, 165670, 256009, 397452, 619647, 967640, 1509297, 2347848, 3643074, 5646004, 8753601, 13591820, 21137644, 32901050, 51205059, 79628272, 123712139

Offset: 1

Author

R. H. Hardin, Mar 13 2015

Keywords

• nonn

Comments

Column 7 of A255992.

Examples

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

Links

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

Crossrefs

Cf. A255992.

Formula

Empirical: a(n) = 2*a(n-1) -a(n-2) +6*a(n-7) -5*a(n-8).

Empirical g.f.: x*(93 - 50*x + 28*x^2 + 50*x^3 + 81*x^4 + 122*x^5 + 174*x^6 - 320*x^7) / (1 - 2*x + x^2 - 6*x^7 + 5*x^8). - Colin Barker, Jan 25 2018