A223364 6X6X6 triangular graph coloring a rectangular array: number of nX2 0..20 arrays where 0..20 label nodes of the fully triangulated graph and every array movement to a horizontal or vertical neighbor moves along an edge of this graph

90, 990, 11610, 139158, 1686042, 20537766, 250834914, 3067525350, 37537522362, 459492912054, 5625465499458, 68876427444102, 843332143519674, 10326055803410934, 126436970898858978, 1548158980998752262

Offset

1,1

Comments

Column 2 of A223370

Links

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

Formula

Empirical: a(n) = 17*a(n-1) -44*a(n-2) -208*a(n-3) +363*a(n-4) +659*a(n-5) -448*a(n-6) -364*a(n-7) +66*a(n-8) +24*a(n-9)

Example

Some solutions for n=3
..4..7....7.11...11..6...11.17...13.12....8.13....0..1....6..3....8.13....8.12
..2..4...12..7...12.11...17.12...12.17....4..8....2..4...11..7....9.14....4..8
..4..2...11.12...11..6...11..7...13.18....5..4....1..3....6..3....8.13....8..7
Vertex neighbors:
0 -> 1 2
1 -> 0 2 3 4
2 -> 0 1 4 5
3 -> 1 4 6 7
4 -> 1 2 3 5 7 8
5 -> 2 4 8 9
6 -> 3 7 10 11
7 -> 3 4 6 8 11 12
8 -> 4 5 7 9 12 13
9 -> 5 8 13 14
10 -> 6 11 15 16
11 -> 6 7 10 12 16 17
12 -> 7 8 11 13 17 18
13 -> 8 9 12 14 18 19
14 -> 9 13 19 20
15 -> 10 16
16 -> 10 11 15 17
17 -> 11 12 16 18
18 -> 12 13 17 19
19 -> 13 14 18 20
20 -> 14 19

Crossrefs

Sequence in context: A173483 A202960 A124167 * A048548 A013427 A013425

Adjacent sequences: A223361 A223362 A223363 * A223365 A223366 A223367

Keyword

nonn

Author

R. H. Hardin Mar 19 2013

Status

approved