A235974 Number of (n+1) X (1+1) 0..2 arrays with the upper median equal to the lower median in every 2 X 2 subblock.

39, 181, 815, 3741, 16999, 77701, 354015, 1615917, 7368343, 33618069, 153332623, 699480765, 3190600647, 14554394789, 66389867839, 302842866765, 1381428661751, 6301472780213, 28744467626991, 131119492345053, 598108270898471

Offset

1,1

Links

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

Formula

Empirical: a(n) = 4*a(n-1) + 7*a(n-2) - 22*a(n-3) + 8*a(n-4).

Empirical g.f.: x*(39 + 25*x - 182*x^2 + 72*x^3) / ((1 - 5*x + 2*x^2)*(1 + x - 4*x^2)). - Colin Barker, Oct 20 2018

Example

Some solutions for n=4:
..2..1....2..1....0..2....2..0....1..0....2..0....2..2....1..2....1..0....0..2
..1..1....2..2....2..2....2..2....1..2....2..2....2..2....1..0....0..0....2..2
..0..2....0..2....2..2....2..1....1..1....2..0....2..0....1..2....2..0....2..0
..2..2....2..2....1..2....2..2....1..1....0..0....0..0....2..2....2..2....0..0
..0..2....1..2....1..0....2..2....2..1....0..1....0..1....2..1....1..2....2..0

Crossrefs

Column 1 of A235981.

Sequence in context: A251335 A251328 A235981 * A258095 A193228 A243578

Adjacent sequences: A235971 A235972 A235973 * A235975 A235976 A235977

Keyword

nonn

Author

R. H. Hardin, Jan 17 2014

Status

approved