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

1,1

Comments

Column 7 of A255992.

Links

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

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

Example

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

Crossrefs

Cf. A255992.

Sequence in context: A249300 A153684 A048257 * A213114 A250366 A306540

Adjacent sequences: A255988 A255989 A255990 * A255992 A255993 A255994

Keyword

nonn

Author

R. H. Hardin, Mar 13 2015

Status

approved