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A281565
Number of 3Xn 0..1 arrays with no element equal to more than two of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.
1
0, 1, 68, 621, 2426, 6955, 16656, 36578, 76332, 153813, 303761, 591012, 1135722, 2162149, 4084667, 7664486, 14298612, 26540583, 49040949, 90250160, 165483166, 302426113, 551024879, 1001197818, 1814514216, 3280781211, 5918961481
OFFSET
1,3
COMMENTS
Row 3 of A281563.
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) -15*a(n-2) +26*a(n-3) -45*a(n-4) +66*a(n-5) -73*a(n-6) +78*a(n-7) -78*a(n-8) +56*a(n-9) -36*a(n-10) +24*a(n-11) -8*a(n-12) for n>20
EXAMPLE
Some solutions for n=4
..0..1..1..0. .0..1..1..1. .0..1..1..0. .0..1..0..1. .0..0..1..1
..1..0..1..1. .0..0..0..0. .1..0..0..1. .0..0..1..1. .0..0..1..1
..1..0..0..0. .1..1..1..0. .0..0..1..1. .1..0..0..1. .0..1..0..1
CROSSREFS
Cf. A281563.
Sequence in context: A027850 A372401 A248467 * A281883 A282333 A244440
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 24 2017
STATUS
approved