A222777 Number of n X 2 0..6 arrays with no element equal to another at a city block distance of exactly two, and new values 0..6 introduced in row major order.

2, 7, 34, 388, 6814, 148168, 3518434, 86343148, 2144234854, 53477637328, 1335790268074, 33384414478708, 834517337010094, 20862096420835288, 521544878361932914, 13038554173140995068, 325963244269451788534

Offset

1,1

Comments

Column 2 of A222779.

Links

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

Formula

Empirical: a(n) = 39*a(n-1) - 399*a(n-2) + 1261*a(n-3) - 900*a(n-4) for n>6.

Conjectures from Colin Barker, Aug 16 2018: (Start)

G.f.: x*(2 - 71*x + 559*x^2 - 667*x^3 - 1779*x^4 + 660*x^5) / ((1 - x)*(1 - 4*x)*(1 - 9*x)*(1 - 25*x)).

a(n) = 9/4 + 2^(2*n-3) + 5*3^(2*n-5) + (7/4)*5^(2*n-5) for n>2.

(End)

Example

Some solutions for n=3:
..0..0....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..1..2....2..2....2..1....2..1....0..2....2..3....2..3....2..3....2..3....2..2
..3..4....1..3....3..3....3..4....3..2....1..0....2..3....4..4....2..0....3..4

Crossrefs

Cf. A222779.

Sequence in context: A000944 A136310 A222868 * A222891 A342411 A231580

Adjacent sequences: A222774 A222775 A222776 * A222778 A222779 A222780

Keyword

nonn

Author

R. H. Hardin, Mar 05 2013

Status

approved