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A166757 Number of nX2 1..4 arrays containing at least one of each value, and all equal values connected. 1
0, 24, 504, 3672, 16272, 53784, 146184, 345240, 733344, 1433880, 2623128, 4543704, 7519536, 11972376, 18439848, 27595032, 40267584, 57466392, 80403768, 110521176, 149516496, 199372824, 262388808, 341210520, 438864864, 558794520, 704894424 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n=1..45

FORMULA

Empirical: a(n) = (4/15)*(n-1)*(8*n^5 -28*n^4 + 97*n^3 - 218*n^2 + 234*n -90).

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

Empirical G.f.: 24*x^2*(x^5 + 8*x^4 + 13*x^3 + 27*x^2 + 14*x + 1)/(1-x)^7.

Empirical E.g.f.: (4/15)*(90 - 90*x + 90*x^2 + 255*x^3 + 285*x^4 + 84*x^5 + 8*x^6)*exp(x) - 24. (End)

EXAMPLE

Some solutions for n=4

...2.1...3.1...3.4...2.4...4.1...1.4...2.2...3.1...1.4...3.1...3.1...2.2...1.4

...3.3...1.1...3.4...2.2...1.1...2.2...4.1...1.1...2.4...3.1...3.2...2.1...1.3

...3.4...1.2...3.4...1.1...3.1...3.2...3.1...2.1...2.3...3.3...2.2...2.2...1.2

...4.4...4.4...1.2...3.1...3.2...3.2...3.1...2.4...2.3...2.4...4.2...4.3...1.1

------

...4.3...2.3...4.4...4.4...3.3...3.3...2.4...3.3...1.3...1.3...3.3...4.4...1.2

...1.3...2.2...1.1...3.4...3.1...4.4...1.1...2.1...2.3...4.4...3.4...3.4...4.4

...2.3...4.4...3.2...3.1...4.1...4.1...1.1...2.4...2.3...4.4...1.1...3.4...4.4

...3.3...1.1...3.2...2.2...2.1...2.2...1.3...4.4...4.4...2.4...2.1...2.1...4.3

CROSSREFS

Sequence in context: A186863 A004383 A112390 * A289833 A242524 A264956

Adjacent sequences: A166754 A166755 A166756 * A166758 A166759 A166760

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 21 2009

STATUS

approved

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Last modified December 8 01:51 EST 2022. Contains 358672 sequences. (Running on oeis4.)