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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 1
90, 990, 11610, 139158, 1686042, 20537766, 250834914, 3067525350, 37537522362, 459492912054, 5625465499458, 68876427444102, 843332143519674, 10326055803410934, 126436970898858978, 1548158980998752262 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 17 22:33 EST 2022. Contains 350410 sequences. (Running on oeis4.)