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A236323
Number of (n+1) X (1+1) 0..1 arrays colored with the sum of the upper and lower median values of each 2 X 2 subblock.
1
16, 32, 60, 120, 252, 496, 972, 1960, 3980, 7872, 15676, 31512, 63260, 125840, 251692, 504456, 1009452, 2014560, 4031900, 8069112, 16136636, 32249392, 64530060, 129075560, 258121932, 516130816, 1032513532, 2064979160, 4129750620
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = a(n-2) + 2*a(n-3) + 8*a(n-4).
Empirical g.f.: 4*x*(4 + 8*x + 11*x^2 + 14*x^3) / ((1 - 2*x)*(1 + 2*x + 3*x^2 + 4*x^3)). - Colin Barker, Oct 21 2018
EXAMPLE
Some solutions for n=5:
..1..1....1..1....1..0....1..1....1..1....0..0....1..1....0..0....0..0....1..1
..0..1....0..1....0..1....0..1....0..1....0..0....0..1....0..1....0..1....1..1
..0..1....0..0....0..0....1..0....1..0....1..1....0..1....0..1....0..1....0..0
..0..0....1..1....1..1....1..1....0..0....1..0....1..1....1..1....1..1....1..0
..1..1....1..0....0..1....0..0....1..1....1..0....0..0....0..0....0..0....1..0
..1..0....0..1....0..1....1..0....1..1....0..0....1..0....0..0....1..0....1..1
CROSSREFS
Sequence in context: A224544 A255994 A204645 * A018923 A264901 A339840
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 22 2014
STATUS
approved