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A297917
Number of n X 2 0..1 arrays with every element equal to 1, 2, 3 or 4 king-move adjacent elements, with upper left element zero.
6
1, 4, 17, 61, 216, 793, 2907, 10622, 38809, 141849, 518472, 1894989, 6926071, 25314486, 92523373, 338168845, 1235992136, 4517496689, 16511251075, 60347893838, 220568887889, 806169548561, 2946514113224, 10769379015141
OFFSET
1,2
COMMENTS
Column 2 of A297923.
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) + 4*a(n-3) + 4*a(n-4) for n>5.
Empirical g.f.: x*(1 + x + 4*x^2 + 2*x^3 - 4*x^4) / (1 - 3*x - x^2 - 4*x^3 - 4*x^4). - Colin Barker, Feb 19 2018
EXAMPLE
Some solutions for n=7:
..0..1. .0..1. .0..1. .0..0. .0..1. .0..0. .0..1. .0..0. .0..0. .0..0
..0..1. .1..0. .0..1. .0..1. .0..1. .0..0. .0..1. .1..1. .0..1. .0..0
..0..1. .1..1. .0..1. .1..0. .0..0. .0..1. .1..0. .1..1. .0..1. .1..0
..0..1. .0..0. .0..0. .0..1. .0..0. .0..1. .0..0. .1..0. .1..0. .0..1
..1..1. .1..0. .1..0. .0..1. .1..0. .1..0. .1..1. .1..0. .0..1. .1..0
..1..0. .0..1. .1..1. .1..0. .0..1. .1..1. .0..1. .1..1. .1..1. .1..0
..0..0. .0..1. .0..0. .1..0. .0..0. .0..0. .1..0. .0..0. .0..0. .0..0
CROSSREFS
Cf. A297923.
Sequence in context: A034331 A107278 A006762 * A202752 A286210 A339286
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 08 2018
STATUS
approved