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A166756 Number of nX2 1..3 arrays containing at least one of each value, and all equal values connected. 1
0, 24, 174, 642, 1716, 3780, 7314, 12894, 21192, 32976, 49110, 70554, 98364, 133692, 177786, 231990, 297744, 376584, 470142, 580146, 708420, 856884, 1027554, 1222542, 1444056, 1694400, 1975974, 2291274, 2642892, 3033516, 3465930, 3943014, 4467744 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n=1..82

FORMULA

Empirical: a(n) = 4*n^4 - 8*n^3 + 11*n^2 - 13*n + 6.

From G. C. Greubel, May 26 2016: (Start)

Empirical G.f.: 6*x^2*(x^3 + 2*x^2 + 9*x + 4)/(1 - x)^5.

Empirical E.g.f.: (6 - 6*x + 15*x^2 + 16*x^3 + 4*x^4)*exp(x) - 6. (End)

EXAMPLE

Some solutions for n=4

...1.1...2.3...1.1...3.2...3.3...2.2...2.2...3.1...2.3...2.3...2.1...3.3...1.1

...1.3...2.1...3.1...2.2...3.1...1.2...2.1...2.1...2.2...2.3...2.1...3.2...2.1

...1.2...2.2...2.1...1.1...3.1...1.1...2.3...1.1...2.1...2.3...1.1...3.1...3.3

...2.2...2.2...1.1...1.1...2.1...3.3...3.3...1.1...1.1...1.1...3.3...1.1...3.3

------

...3.3...1.3...1.2...1.2...3.3...3.1...3.2...3.3...2.1...3.2...1.1...2.2...1.1

...3.1...1.1...1.2...1.3...3.3...3.3...3.3...3.2...1.1...3.3...1.3...2.1...2.2

...1.1...1.2...1.1...3.3...1.1...3.3...3.3...2.2...3.1...3.3...1.1...2.2...2.2

...2.1...2.2...3.1...3.3...2.1...2.2...1.1...2.1...1.1...1.3...2.2...3.2...2.3

CROSSREFS

Sequence in context: A223291 A221069 A272125 * A268623 A209716 A209709

Adjacent sequences:  A166753 A166754 A166755 * A166757 A166758 A166759

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 21 2009

STATUS

approved

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Last modified October 4 03:29 EDT 2022. Contains 357237 sequences. (Running on oeis4.)