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A266050 Number of n X 3 integer arrays with each element equal to the number of horizontal and antidiagonal neighbors less than or equal to itself. 1
2, 12, 20, 54, 120, 284, 660, 1540, 3592, 8376, 19536, 45560, 106256, 247808, 577936, 1347856, 3143456, 7331136, 17097600, 39874848, 92995712, 216883648, 505813824, 1179653824, 2751176576, 6416265856, 14963949568, 34898770048, 81390554368 (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) + 2*a(n-2) - 2*a(n-3) - 2*a(n-4).

Empirical g.f.: 2*x*(1 + 4*x - 4*x^2 - 3*x^3) / (1 - 2*x - 2*x^2 + 2*x^3 + 2*x^4). - Colin Barker, Jan 09 2019

EXAMPLE

Some solutions for n=4:

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

..1..0..2....2..1..2....2..0..2....2..0..2....1..4..1....1..4..0....2..0..2

..2..0..2....0..1..2....2..0..2....2..0..1....1..0..2....0..4..1....2..0..2

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

CROSSREFS

Column 3 of A266055.

Sequence in context: A226399 A121859 A145622 * A291698 A174478 A331947

Adjacent sequences:  A266047 A266048 A266049 * A266051 A266052 A266053

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 20 2015

STATUS

approved

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Last modified May 15 03:16 EDT 2021. Contains 343909 sequences. (Running on oeis4.)