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A251204 Number of (n+1) X (2+1) 0..2 arrays with every 2 X 2 subblock summing to a nonzero multiple of 2. 1
180, 1246, 8870, 65040, 489772, 3775022, 29664576, 236740252, 1912108322, 15584536740, 127880485540, 1054537633526, 8727275684760, 72413361371620, 601955189383922, 5010545177519292, 41746084890460636, 348047155647060662 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 18*a(n-1) - 90*a(n-2) + 7*a(n-3) + 576*a(n-4) + 210*a(n-5) - 180*a(n-6).

Empirical g.f.: 2*x*(90 - 997*x + 1321*x^2 + 8130*x^3 + 2475*x^4 - 2430*x^5) / ((1 - 6*x)*(1 - 5*x - 5*x^2)*(1 - 7*x - 12*x^2 + 6*x^3)). - Colin Barker, Nov 27 2018

EXAMPLE

Some solutions for n=4:

..2..2..0....0..2..2....2..2..0....1..1..1....1..0..2....0..2..2....2..0..2

..0..0..0....2..0..2....2..2..0....0..2..2....1..0..2....0..2..2....2..2..0

..0..2..0....1..1..1....2..0..0....2..2..0....1..2..0....2..0..2....0..2..0

..0..2..2....2..2..2....0..2..0....2..2..2....1..2..0....0..2..0....2..0..0

..2..2..0....2..0..2....0..0..0....2..0..2....1..0..2....1..1..1....1..1..1

CROSSREFS

Column 2 of A251210.

Sequence in context: A032774 A032776 A251255 * A225933 A225932 A081380

Adjacent sequences:  A251201 A251202 A251203 * A251205 A251206 A251207

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 30 2014

STATUS

approved

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Last modified June 16 11:12 EDT 2019. Contains 324152 sequences. (Running on oeis4.)