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A280804
Number of nX2 0..1 arrays with no element equal to more than two of its horizontal, vertical and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.
1
0, 1, 3, 18, 72, 284, 1047, 3722, 12816, 43077, 142046, 461225, 1478635, 4689871, 14740063, 45963889, 142346346, 438168498, 1341507977, 4087399361, 12399650175, 37467705018, 112808649521, 338530408321, 1012834966758, 3021810804515
OFFSET
1,3
COMMENTS
Column 2 of A280810.
LINKS
FORMULA
Empirical: a(n) = 9*a(n-1) -30*a(n-2) +48*a(n-3) -45*a(n-4) +18*a(n-5) +44*a(n-6) -60*a(n-7) +30*a(n-8) -2*a(n-9) -51*a(n-10) +21*a(n-11) +13*a(n-12) -3*a(n-13) +18*a(n-14) +7*a(n-15) -9*a(n-16) -6*a(n-17) -a(n-18)
EXAMPLE
Some solutions for n=4
..0..0. .0..1. .0..0. .0..0. .0..1. .0..1. .0..0. .0..1. .0..0. .0..1
..1..1. .1..1. .1..0. .0..1. .1..0. .1..1. .0..0. .0..0. .0..1. .0..0
..0..0. .0..0. .0..0. .0..1. .0..0. .0..1. .1..1. .1..1. .0..0. .0..1
..0..0. .0..0. .1..0. .1..1. .0..1. .1..1. .0..1. .1..1. .0..1. .0..0
CROSSREFS
Cf. A280810.
Sequence in context: A135070 A073961 A305623 * A152897 A059393 A301820
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 08 2017
STATUS
approved