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A301819
Number of nX4 0..1 arrays with every element equal to 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero.
1
2, 8, 25, 68, 177, 457, 1183, 3075, 8018, 20947, 54782, 143348, 375200, 982178, 2571247, 6731462, 17623023, 46137475, 120789253, 316230117, 827900912, 2167472413, 5674516100, 14856075638, 38893710542, 101825055692, 266581456213
OFFSET
1,1
COMMENTS
Column 4 of A301823.
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) -13*a(n-2) +13*a(n-3) -6*a(n-4) +a(n-5)
EXAMPLE
Some solutions for n=5
..0..0..1..1. .0..0..1..1. .0..0..1..1. .0..0..1..1. .0..0..1..1
..1..1..0..0. .0..1..0..0. .0..1..0..1. .0..0..0..0. .0..0..1..1
..0..0..1..1. .1..0..1..1. .1..0..1..0. .1..1..0..1. .0..0..1..0
..1..1..0..1. .0..1..0..0. .0..1..0..1. .1..0..1..1. .1..1..0..1
..0..0..1..1. .1..0..1..1. .1..0..1..1. .0..0..0..0. .0..0..1..1
CROSSREFS
Cf. A301823.
Sequence in context: A370637 A066374 A193048 * A119854 A176855 A309237
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 27 2018
STATUS
approved