A223460 6 X 6 X 6 triangular graph without horizontal edges coloring a rectangular array: number of n X 1 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.

21, 60, 190, 600, 1946, 6264, 20440, 66208, 216452, 702768, 2298936, 7470944, 24444168, 79466336, 260022112, 845441152, 2766427344, 8995380672, 29434608608, 95712808320, 313191301792, 1018418848640, 3332470833536, 10836405217792

Offset

1,1

Comments

Column 1 of A223467.

Links

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

Formula

Empirical: a(n) = 20*a(n-2) -126*a(n-4) +304*a(n-6) -252*a(n-8) +80*a(n-10) -8*a(n-12).

Example

Some solutions for n=3
..1...15...11....1...11....6...12....7....4....4....8....9....1....2....7...13
..0...10....7....3...16...11...18...11....8....8....5....5....3....4....4...19
..2...15...11....6...10....6...13....7...12....5....9....9....1....8....2...14

Crossrefs

Cf. A223467.

Sequence in context: A370109 A223467 A051873 * A219690 A325319 A069133

Adjacent sequences: A223457 A223458 A223459 * A223461 A223462 A223463

Keyword

nonn

Author

R. H. Hardin Mar 20 2013

Status

approved