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A280897 Number of n X 3 0..2 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards. 1
0, 10, 646, 22632, 610448, 14262832, 304584096, 6117000704, 117496694272, 2181977379072, 39462274293248, 698659360847872, 12154771113160704, 208386384523096064, 3528538532937736192, 59112926060691652608 (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) = 42*a(n-1) - 564*a(n-2) + 2072*a(n-3) + 4512*a(n-4) + 2688*a(n-5) + 512*a(n-6) for n>8.

Empirical g.f.: 2*x^2*(5 + 113*x + 570*x^2 + 1764*x^3 + 2416*x^4 + 1344*x^5 + 256*x^6) / (1 - 14*x - 8*x^2)^3. - Colin Barker, Feb 14 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 3 of A280902.

Sequence in context: A209472 A132543 A261328 * A099024 A126680 A249848

Adjacent sequences:  A280894 A280895 A280896 * A280898 A280899 A280900

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 10 2017

STATUS

approved

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Last modified May 11 13:41 EDT 2021. Contains 343791 sequences. (Running on oeis4.)