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.

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

R. H. Hardin, Table of n, a(n) for n = 1..210

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 A023053

Adjacent sequences: A222937 A222938 A222939 * A222941 A222942 A222943

Keyword

nonn

Author

R. H. Hardin, Mar 09 2013

Status

approved