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A301995
Number of nX4 0..1 arrays with every element equal to 1, 2 or 4 horizontally or antidiagonally adjacent elements, with upper left element zero.
1
2, 8, 26, 74, 200, 530, 1394, 3656, 9578, 25082, 65672, 171938, 450146, 1178504, 3085370, 8077610, 21147464, 55364786, 144946898, 379475912, 993480842, 2600966618, 6809419016, 17827290434, 46672452290, 122190066440, 319897747034
OFFSET
1,1
COMMENTS
Column 4 of A301999.
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) -4*a(n-2) +a(n-3)
EXAMPLE
Some solutions for n=5
..0..0..1..1. .0..0..1..0. .0..0..1..1. .0..0..1..1. .0..0..1..1
..0..0..0..0. .0..1..0..0. .1..1..0..0. .0..1..0..1. .0..1..0..0
..1..1..1..1. .1..1..0..0. .0..0..0..0. .1..0..1..1. .1..1..0..0
..0..0..1..1. .1..1..0..0. .0..0..1..1. .0..0..1..0. .1..1..0..0
..0..0..1..1. .1..1..1..1. .1..1..0..0. .1..1..0..0. .1..1..1..1
CROSSREFS
Cf. A301999.
Sequence in context: A136594 A268502 A167826 * A325926 A097040 A302237
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 30 2018
STATUS
approved