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A220324 Equals two maps: number of n X 3 binary arrays indicating the locations of corresponding elements equal to exactly two of their horizontal and antidiagonal neighbors in a random 0..1 n X 3 array. 1
2, 16, 92, 508, 2788, 15316, 84196, 462940, 2545492, 13996468, 76959844, 423164812, 2326777444, 12793817140, 70346976484, 386803802332, 2126845944052, 11694491219668, 64302318307108, 353567167818892, 1944093859291588 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A220328.

LINKS

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

FORMULA

Empirical: a(n) = 7*a(n-1) - 9*a(n-2) + 3*a(n-3) + 6*a(n-4).

Empirical g.f.: 2*x*(1 + x - x^2 + x^3) / (1 - 7*x + 9*x^2 - 3*x^3 - 6*x^4). - Colin Barker, Jul 31 2018

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A220328.

Sequence in context: A208550 A214824 A317451 * A208002 A220932 A207558

Adjacent sequences:  A220321 A220322 A220323 * A220325 A220326 A220327

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 10 2012

STATUS

approved

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Last modified August 14 09:27 EDT 2022. Contains 356110 sequences. (Running on oeis4.)