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A222940
Number of n X 2 0..4 arrays with no element equal to another at a city block distance of exactly two, and new values 0..4 introduced in row major order.
1
2, 7, 33, 273, 2433, 21873, 196833, 1771473, 15943233, 143489073, 1291401633, 11622614673, 104603532033, 941431788273, 8472886094433, 76255974849873, 686303773648833, 6176733962839473, 55590605665555233, 500315450989997073
OFFSET
1,1
COMMENTS
Column 2 of A222944.
LINKS
FORMULA
Empirical: a(n) = 10*a(n-1) - 9*a(n-2) for n>4.
Conjectures from Colin Barker, Aug 16 2018: (Start)
G.f.: x*(2 - 13*x - 19*x^2 + 6*x^3) / ((1 - x)*(1 - 9*x)).
a(n) = 3 + 10*3^(2*n-5) for n>2
(End)
EXAMPLE
Some solutions for n=3:
..0..1....0..1....0..1....0..0....0..1....0..1....0..0....0..0....0..1....0..1
..2..3....2..3....2..3....1..1....2..2....2..3....1..1....1..2....2..3....0..1
..1..4....4..0....4..4....2..2....1..0....2..0....2..3....3..3....1..0....2..3
CROSSREFS
Cf. A222944.
Sequence in context: A143889 A350758 A241767 * A227120 A353343 A376055
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 09 2013
STATUS
approved