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A301657
Number of nX3 0..1 arrays with every element equal to 0, 1 or 4 horizontally or vertically adjacent elements, with upper left element zero.
1
3, 4, 6, 9, 15, 26, 46, 83, 151, 276, 506, 929, 1707, 3138, 5770, 10611, 19515, 35892, 66014, 121417, 223319, 410746, 755478, 1389539, 2555759, 4700772, 8646066, 15902593, 29249427, 53798082, 98950098, 181997603, 334745779, 615693476
OFFSET
1,1
COMMENTS
Column 3 of A301662.
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) -a(n-4)
EXAMPLE
Some solutions for n=5
..0..0..1. .0..1..0. .0..1..0. .0..1..0. .0..1..0. .0..1..0. .0..1..1
..1..1..0. .1..1..1. .0..1..0. .1..0..1. .1..1..1. .1..0..1. .1..0..0
..0..0..1. .0..1..0. .1..0..1. .1..0..1. .0..1..0. .0..0..0. .0..1..1
..1..1..0. .1..0..1. .1..0..1. .0..1..0. .1..0..1. .1..0..1. .1..0..0
..0..0..1. .0..1..0. .0..1..0. .0..1..0. .1..0..1. .0..1..0. .0..1..1
CROSSREFS
Cf. A301662.
Sequence in context: A291866 A332829 A173270 * A241342 A018830 A102934
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 25 2018
STATUS
approved