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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
1, 4, 55, 1368, 34442, 868994, 21916090, 552801398, 13943026782, 351682327314, 8870382111250, 223735362633678, 5643217340398022, 142337380859578634, 3590138049351706810, 90553101869397071558, 2283996915742293943662 (list; graph; refs; listen; history; text; internal format)
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

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Last modified June 24 17:11 EDT 2021. Contains 345417 sequences. (Running on oeis4.)