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A317857
Number of nX2 0..1 arrays with every element unequal to 1, 2 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.
3
1, 3, 6, 10, 21, 46, 102, 220, 491, 1077, 2393, 5271, 11682, 25799, 57090, 126209, 279123, 617274, 1364930, 3018713, 6675002, 14762294, 32643544, 72191407, 159639957, 353036505, 780698639, 1726457594, 3817890631, 8442936930
OFFSET
1,2
COMMENTS
Column 2 of A317863.
LINKS
FORMULA
Empirical: a(n) = a(n-1) +4*a(n-2) -2*a(n-3) -2*a(n-4) +a(n-5) -4*a(n-6) +4*a(n-7) -a(n-8)
EXAMPLE
Some solutions for n=5
..0..0. .0..1. .0..0. .0..1. .0..0. .0..0. .0..1. .0..1. .0..0. .0..1
..1..0. .0..1. .1..0. .1..0. .1..0. .1..1. .1..1. .1..1. .1..1. .1..1
..0..0. .0..1. .0..0. .1..1. .0..0. .1..1. .0..1. .0..0. .1..0. .1..0
..1..0. .0..1. .0..1. .0..1. .1..1. .0..1. .1..0. .0..0. .1..1. .0..0
..0..1. .0..1. .0..0. .1..0. .1..0. .1..0. .1..1. .1..1. .1..0. .0..1
CROSSREFS
Cf. A317863.
Sequence in context: A068709 A068804 A117834 * A346733 A220827 A063015
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 09 2018
STATUS
approved