A207094 Number of 0..2 arrays x(0..n-1) of n elements with each no smaller than the sum of its two previous neighbors modulo 3.

3, 6, 12, 26, 55, 115, 239, 498, 1038, 2162, 4502, 9375, 19523, 40655, 84659, 176292, 367107, 764456, 1591886, 3314907, 6902887, 14374415, 29932954, 62331700, 129798109, 270288619, 562842849, 1172051097, 2440652442, 5082358916

Offset

1,1

Comments

Column 2 of A207100.

Links

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

Formula

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

Empirical g.f.: x*(3 + 2*x^3 - x^5 - x^8) / ((1 - x)*(1 - x - x^2 - x^3 - 2*x^4 - 2*x^5 - x^6 - x^7 - x^8)). - Colin Barker, Jun 18 2018

Example

Some solutions for n=5:
..1....0....1....0....0....0....0....0....1....0....1....1....0....0....0....0
..2....1....2....1....1....0....0....2....1....0....2....2....1....1....0....0
..2....1....1....1....2....0....2....2....2....0....1....2....2....2....0....0
..1....2....1....2....2....0....2....1....2....1....0....1....1....1....0....0
..2....2....2....0....1....1....2....2....2....2....1....0....2....0....0....2

Crossrefs

Cf. A207100.

Sequence in context: A274476 A274059 A092886 * A135035 A054195 A054190

Adjacent sequences: A207091 A207092 A207093 * A207095 A207096 A207097

Keyword

nonn

Author

R. H. Hardin, Feb 15 2012

Status

approved