A223461 6X6X6 triangular graph without horizontal edges coloring a rectangular array: number of nX2 0..20 arrays where 0..20 label nodes of a graph with edges 0,1 0,2 1,3 1,4 2,4 2,5 3,6 3,7 4,7 4,8 5,8 5,9 6,10 6,11 7,11 7,12 8,12 8,13 9,13 9,14 10,15 10,16 11,16 11,17 12,17 12,18 13,18 13,19 14,19 14,20 and every array movement to a horizontal or vertical neighbor moves along an edge of this graph

60, 400, 2840, 20588, 150952, 1113460, 8242836, 61154044, 454323480, 3378142656, 25132084932, 187038782168, 1392302053188, 10365718449436, 77180451082908, 574702146451168, 4279535041962520, 31868564543578604, 237321202996080216

Offset

1,1

Comments

Column 2 of A223467

Links

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

Formula

Empirical: a(n) = 20*a(n-1) -137*a(n-2) +299*a(n-3) +529*a(n-4) -2784*a(n-5) +973*a(n-6) +6475*a(n-7) -4402*a(n-8) -4888*a(n-9) +2878*a(n-10) +428*a(n-11) -408*a(n-12) +52*a(n-13)

Example

Some solutions for n=3
.12..7...12..7....1..3...11.17...18.13...10..6....4..2...12..8....8.13....9.14
..8.12....8.12....3..7....7.12...12..8...16.11....8..5...18.12....4..8...13.19
.13..8....4..8....7.11...12.18...18.13...10..6...12..8...12..8....1..4....8.13

Crossrefs

Sequence in context: A088942 A135037 A020868 * A088943 A097387 A057096

Adjacent sequences: A223458 A223459 A223460 * A223462 A223463 A223464

Keyword

nonn

Author

R. H. Hardin Mar 20 2013

Status

approved