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A231081 Number of 2 X n 0..2 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 3 and at least one element with value (x(i,j)-1) mod 3, and upper left element zero. 1
0, 2, 14, 40, 356, 1840, 10128, 60808, 337016, 1932520, 11047240, 62712776, 358084712, 2039935624, 11622103656, 66251217992, 377502949416, 2151360049288, 12260476416616, 69868714030792, 398172491295656, 2269109338791176 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = 3*a(n-1) + 12*a(n-2) + 30*a(n-3) - 64*a(n-4) + 16*a(n-5).

Empirical g.f.: x*2*(1 + 4*x - 13*x^2 + 4*x^3) / (1 - 3*x - 12*x^2 - 30*x^3 + 64*x^4 - 16*x^5). - Colin Barker, Sep 26 2018

EXAMPLE

Some solutions for n=3:

..0..1..0....0..3..0....0..3..2....0..3..2....0..3..0....0..1..2....0..3..2

..0..3..2....2..1..0....2..1..2....0..1..0....2..1..2....0..3..0....2..1..0

CROSSREFS

Row 2 of A231080.

Sequence in context: A290124 A192349 A230801 * A152670 A109137 A192375

Adjacent sequences:  A231078 A231079 A231080 * A231082 A231083 A231084

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 03 2013

STATUS

approved

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Last modified March 29 13:55 EDT 2020. Contains 333107 sequences. (Running on oeis4.)