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A233637 Number of (n+1) X (1+1) 0..2 arrays with every 2 X 2 subblock having the sum of the squares of the edge differences equal to 2. 1
24, 90, 324, 1188, 4320, 15768, 57456, 209520, 763776, 2784672, 10152000, 37012032, 134936064, 491944320, 1793505024, 6538675968, 23838382080, 86908819968, 316847932416, 1155148784640, 4211385163776, 15353663035392, 55975637053440 (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) = 2*a(n-1) + 6*a(n-2).

Conjectures from Colin Barker, Oct 11 2018: (Start)

G.f.: 6*x*(4 + 7*x) / (1 - 2*x - 6*x^2).

a(n) = ((1-sqrt(7))^n*(-17+7*sqrt(7)) + (1+sqrt(7))^n*(17+7*sqrt(7))) / (2*sqrt(7)).

(End)

EXAMPLE

Some solutions for n=5:

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

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

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

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

..1..1....1..1....1..1....1..0....1..1....0..1....1..1....1..1....1..1....1..0

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

CROSSREFS

Column 1 of A233644.

Sequence in context: A233644 A010012 A256718 * A179962 A076799 A297540

Adjacent sequences:  A233634 A233635 A233636 * A233638 A233639 A233640

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 14 2013

STATUS

approved

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Last modified August 13 05:18 EDT 2022. Contains 356077 sequences. (Running on oeis4.)