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A202884
Number of nX3 0..2 arrays with every nonzero element less than or equal to some horizontal or vertical neighbor.
1
9, 265, 5493, 109119, 2223723, 45332961, 922352267, 18770352883, 382034229103, 7775324294349, 158245814846079, 3220677883878199, 65548442623908105, 1334066131775449299, 27151407675046583355, 552595506856781602893
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 22*a(n-1) -73*a(n-2) +857*a(n-3) -1769*a(n-4) +12671*a(n-5) +21249*a(n-6) +11663*a(n-7) -43772*a(n-8) -233931*a(n-9) -841906*a(n-10) -520038*a(n-11) -711742*a(n-12) +722084*a(n-13) +4070420*a(n-14) +788112*a(n-15) -3390432*a(n-16) -1162224*a(n-17) +645120*a(n-18) +248832*a(n-19)
EXAMPLE
Some solutions for n=3
..1..1..1....1..2..2....0..0..2....0..2..2....2..1..1....1..0..0....0..0..2
..1..0..2....1..2..1....0..1..2....0..1..1....2..1..0....2..2..2....2..2..2
..1..2..2....0..2..0....0..2..2....2..2..1....1..1..0....2..1..1....0..2..2
CROSSREFS
Column 3 of A202889.
Sequence in context: A003387 A177393 A081059 * A188963 A306535 A144684
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 25 2011
STATUS
approved