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A235895
Number of (n+1) X (1+1) 0..2 arrays with the minimum plus the maximum equal to the lower median plus the upper median in every 2 X 2 subblock.
1
33, 125, 473, 1797, 6849, 26189, 100457, 386517, 1491537, 5771933, 22396025, 87120549, 339708129, 1327583213, 5199036809, 20399760501, 80187289713, 315721128509, 1244976918425, 4916128826181, 19437363570945, 76940441387405
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 7*a(n-1) -10*a(n-2) -8*a(n-3).
Conjectures from Colin Barker, Oct 20 2018: (Start)
G.f.: x*(33 - 106*x - 72*x^2) / ((1 - 4*x)*(1 - 3*x - 2*x^2)).
a(n) = 4^(1+n) + (2^(-1-n)*((3-sqrt(17))^n*(-19+5*sqrt(17)) + (3+sqrt(17))^n*(19+5*sqrt(17)))) / sqrt(17).
(End)
EXAMPLE
Some solutions for n=4:
..2..1....1..1....0..2....1..0....2..1....2..1....1..0....2..2....1..0....2..2
..0..1....2..2....1..1....1..2....0..1....1..0....0..1....0..0....0..1....0..0
..1..0....2..2....1..1....1..2....2..1....1..2....1..0....1..1....2..1....0..0
..1..2....0..0....1..1....0..1....1..2....1..0....2..1....2..0....1..0....1..1
..2..1....0..0....1..1....1..2....1..2....1..2....2..1....1..1....1..0....2..2
CROSSREFS
Column 1 of A235902.
Sequence in context: A301633 A039440 A235902 * A010020 A007419 A158575
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 16 2014
STATUS
approved