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A280436
Number of nX4 0..1 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.
1
2, 20, 42, 80, 138, 232, 386, 640, 1062, 1764, 2934, 4884, 8134, 13548, 22562, 37560, 62498, 103936, 172746, 286936, 476318, 790220, 1310222, 2171180, 3595918, 5952452, 9848346, 16286240, 26920122, 44477464, 73454354, 121259824, 200099094
OFFSET
1,1
COMMENTS
Column 4 of A280440.
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) -4*a(n-2) -2*a(n-3) +4*a(n-4) -a(n-6) for n>7.
Empirical g.f.: 2*x + 2*x^2*(10-19*x-4*x^2+13*x^3+x^5+2*x^4) / ( (x-1)^2*(x^2+x-1)^2 ). - R. J. Mathar, Jan 04 2017
EXAMPLE
Some solutions for n=4
..0..1..1..0. .0..1..0..1. .0..1..1..0. .0..0..1..0. .0..1..0..1
..1..0..0..1. .1..0..0..0. .1..0..0..1. .1..0..1..0. .1..0..1..0
..0..1..1..0. .0..1..0..1. .0..1..1..0. .0..1..0..1. .0..1..0..1
..1..0..1..0. .1..0..1..0. .0..1..0..1. .1..0..1..0. .1..0..0..1
CROSSREFS
Cf. A280440.
Sequence in context: A293930 A357485 A194999 * A266842 A254542 A202602
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 03 2017
STATUS
approved