A202884 Number of nX3 0..2 arrays with every nonzero element less than or equal to some horizontal or vertical neighbor.

9, 265, 5493, 109119, 2223723, 45332961, 922352267, 18770352883, 382034229103, 7775324294349, 158245814846079, 3220677883878199, 65548442623908105, 1334066131775449299, 27151407675046583355, 552595506856781602893

Offset

1,1

Links

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

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

Adjacent sequences: A202881 A202882 A202883 * A202885 A202886 A202887

Keyword

nonn

Author

R. H. Hardin, Dec 25 2011

Status

approved