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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
1
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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 20 2013
STATUS
approved