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A301836
Number of n X 3 0..1 arrays with every element equal to 0, 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero.
1
4, 25, 139, 773, 4299, 23909, 132971, 739525, 4112907, 22874149, 127215787, 707517317, 3934894923, 21884125925, 121709722091, 676895047237, 3764587553931, 20936952499621, 116441967065899, 647598149464325
OFFSET
1,1
COMMENTS
Column 3 of A301841.
LINKS
FORMULA
Empirical: a(n) = 7*a(n-1) -8*a(n-2) for n > 3.
EXAMPLE
Some solutions for n=5
..0..0..0. .0..1..0. .0..1..1. .0..1..0. .0..1..1. .0..0..1. .0..0..1
..1..1..0. .1..1..1. .0..1..0. .1..0..0. .0..0..0. .1..0..0. .1..0..1
..1..1..0. .0..0..1. .0..1..0. .1..1..0. .1..0..1. .1..0..0. .1..0..0
..0..1..0. .1..0..1. .1..1..1. .0..1..0. .1..0..1. .1..0..0. .1..1..0
..0..1..1. .1..0..1. .0..1..1. .1..1..1. .1..1..0. .1..0..1. .1..1..0
CROSSREFS
Cf. A301841.
Sequence in context: A015533 A207410 A278275 * A275177 A079291 A173612
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 27 2018
STATUS
approved