A206384 Number of n X 3 0..6 arrays with no element equal to another within a city block distance of two, and new values 0..6 introduced in row major order.

1, 4, 55, 1368, 34442, 868994, 21916090, 552801398, 13943026782, 351682327314, 8870382111250, 223735362633678, 5643217340398022, 142337380859578634, 3590138049351706810, 90553101869397071558, 2283996915742293943662

Offset

1,2

Comments

Column 3 of A206389.

Links

R. H. Hardin, Table of n, a(n) for n = 1..150

Formula

Empirical: a(n) = 21*a(n-1) + 131*a(n-2) - 637*a(n-3) + 486*a(n-4) for n>6.

Empirical g.f.: x*(1 - 17*x - 160*x^2 + 326*x^3 + 571*x^4 - 405*x^5) / ((1 - x)*(1 - 20*x - 151*x^2 + 486*x^3)). - Colin Barker, Jun 15 2018

Example

Some solutions for n=4:
..0..1..2....0..1..2....0..1..2....0..1..2....0..1..2....0..1..2....0..1..2
..3..4..0....2..3..4....2..3..4....2..3..4....2..3..4....2..3..0....3..4..5
..1..2..5....4..5..6....4..5..6....4..5..0....1..0..5....1..4..5....5..2..1
..6..0..1....3..0..1....3..1..0....3..1..6....4..2..1....6..0..1....1..6..4

Crossrefs

Cf. A206389.

Sequence in context: A258793 A195634 A322627 * A271715 A099122 A001500

Adjacent sequences: A206381 A206382 A206383 * A206385 A206386 A206387

Keyword

nonn

Author

R. H. Hardin, Feb 07 2012

Status

approved