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A317891
Number of nX3 0..1 arrays with every element unequal to 2, 3 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.
1
0, 1, 4, 13, 59, 252, 1074, 4633, 19933, 85732, 368847, 1586817, 6826551, 29368380, 126345008, 543545426, 2338372742, 10059853024, 43278232785, 186186164251, 800986675100, 3445904026216, 14824534451888, 63776245668953
OFFSET
1,3
COMMENTS
Column 3 of A317896.
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) +8*a(n-3) -10*a(n-4) +3*a(n-5) -17*a(n-6) -7*a(n-7) -21*a(n-8) +6*a(n-9) +10*a(n-10) +4*a(n-11) -18*a(n-12) -21*a(n-13) -9*a(n-14) -a(n-15) +2*a(n-16) for n>18
EXAMPLE
Some solutions for n=5
..0..1..0. .0..1..1. .0..1..0. .0..1..1. .0..1..0. .0..1..0. .0..1..0
..1..0..1. .1..0..0. .1..1..0. .1..0..0. .1..1..0. .1..1..0. .1..0..1
..0..1..0. .0..1..0. .0..1..0. .0..1..1. .0..0..1. .0..0..1. .1..0..0
..1..1..1. .1..1..1. .0..1..1. .0..1..0. .1..0..1. .0..1..0. .0..0..1
..0..1..0. .0..1..0. .0..1..0. .1..0..1. .0..1..0. .1..0..1. .1..1..0
CROSSREFS
Cf. A317896.
Sequence in context: A219572 A026663 A149486 * A115455 A241470 A219367
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 10 2018
STATUS
approved