A250381 Number of length n+3 0..2 arrays with no four consecutive terms having the maximum of any two terms equal to the minimum of the remaining two terms.

42, 78, 146, 274, 514, 966, 1816, 3414, 6418, 12066, 22688, 42658, 80208, 150808, 283566, 533182, 1002538, 1885048, 3544452, 6664608, 12531430, 23562750, 44304934, 83306386, 156640636, 294530672, 553804746, 1041316906, 1957983912

Offset

1,1

Comments

Column 2 of A250387.

Links

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

Formula

From Colin Barker, Aug 20 2017: (Start)

Empirical recurrence: a(n) = a(n-1) +2*a(n-2) -a(n-3) +3*a(n-4) -a(n-5) -7*a(n-6) +a(n-7) +a(n-10).

Empirical g.f.: 2*x*(21 + 18*x - 8*x^2 + 7*x^3 - 50*x^4 - 71*x^5 + 15*x^6 + 4*x^7 + 7*x^8 + 12*x^9) / (1 - x - 2*x^2 + x^3 - 3*x^4 + x^5 + 7*x^6 - x^7 - x^10).

(End)

Example

Some solutions for n=6
..1....1....2....2....1....0....2....1....0....0....1....0....1....0....2....1
..0....2....0....0....0....0....1....2....1....2....0....2....0....1....0....0
..0....2....1....2....1....1....2....2....2....1....2....2....2....0....0....2
..2....1....2....0....0....2....0....0....0....0....0....1....0....1....1....0
..2....0....0....1....1....2....2....1....2....2....2....0....1....0....1....2
..0....2....2....0....0....1....1....2....1....2....0....2....2....1....0....1
..1....2....1....2....2....0....2....0....0....1....1....0....0....0....0....0
..2....0....2....2....0....2....1....0....2....0....2....2....0....2....1....2
..2....1....1....0....2....2....2....2....0....2....2....0....2....2....1....0

Crossrefs

Sequence in context: A068700 A303283 A135850 * A153644 A172437 A160283

Adjacent sequences: A250378 A250379 A250380 * A250382 A250383 A250384

Keyword

nonn

Author

R. H. Hardin, Nov 20 2014

Status

approved