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A223459
6X6X6 triangular graph without horizontal edges coloring a rectangular array: number of n X n 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
0
21, 400, 47100, 31075684, 116111266332, 2412122721426324, 280173531066504459408, 180359138791051357960964956, 646396187061902362932292802186560
OFFSET
1,1
COMMENTS
Diagonal of A223467
EXAMPLE
Some solutions for n=3
..6.11..6....8.13..8....7.12..7....7..4..1...12.18.12....1..0..2...14.19.13
.11..7.11...13..8..5....4..8..4....4..1..4...17.12..7....0..2..0....9.14..9
..6.11..6....8.13..9....8..5..2....1..3..7...11.17.11....1..0..1...13..9.13
CROSSREFS
Sequence in context: A015677 A285396 A113363 * A240655 A014903 A219308
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 20 2013
STATUS
approved