A249701 Number of length n+3 0..2 arrays with every four consecutive terms having the maximum of some two terms equal to the minimum of the remaining two terms.

39, 69, 125, 221, 377, 659, 1177, 2119, 3805, 6857, 12437, 22681, 41475, 76011, 139645, 257161, 474439, 876539, 1621387, 3002407, 5564769, 10321599, 19156321, 35571383, 66081147, 122803551, 228283091, 424467169, 789412673, 1468380739

Offset: 1

Author

R. H. Hardin, Nov 04 2014

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 2 of A249707.

Formula

Empirical: a(n) = 3*a(n-1) - 3*a(n-2) + 2*a(n-3) + 2*a(n-4) - 5*a(n-5) + a(n-6) -a(n-7) - 2*a(n-8) + 2*a(n-10).

Empirical g.f.: x*(39 - 48*x + 35*x^2 - 25*x^3 - 127*x^4 - 2*x^5 - 55*x^6 - 36*x^7 + 34*x^8 + 54*x^9) / ((1 + x)*(1 - 2*x + 2*x^2 - 2*x^3)*(1 - 2*x + x^2 - x^3 - x^4 + x^6)). - Colin Barker, Nov 09 2018