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A166815 Number of nX2 1..4 arrays containing at least one of each value, all equal values connected, rows considered as a single number in nondecreasing order, and columns considered as a single number in increasing order. 1
0, 8, 67, 268, 772, 1836, 3843, 7336, 13056, 21984, 35387, 54868, 82420, 120484, 172011, 240528, 330208, 445944, 593427, 779228, 1010884, 1296988, 1647283, 2072760, 2585760, 3200080, 3931083, 4795812, 5813108, 7003732, 8390491, 9998368 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n=1..44

FORMULA

Empirical: a(n)=(n^6+18*n^5+115*n^4+60*n^3-566*n^2+372*n)/180.

Empirical: G.f.: x^2*(-8-11*x+33*x^2-23*x^3+5*x^4) / (x-1)^7 . - R. J. Mathar, Nov 23 2015

EXAMPLE

Some solutions for n=4

...1.3...1.1...1.4...1.2...1.3...1.3...1.2...1.2...1.3...1.1...1.2...1.1...1.1

...1.3...1.4...2.4...3.2...1.4...3.3...2.2...3.2...3.3...1.2...1.4...1.1...1.1

...1.4...1.4...2.4...3.3...2.4...3.3...3.3...3.2...4.2...3.3...1.4...1.4...2.3

...2.2...2.3...3.4...4.3...2.4...4.2...3.4...3.4...4.4...4.3...3.3...3.2...2.4

------

...1.2...1.1...1.2...1.2...1.3...2.3...1.3...1.1...2.4...1.2...1.1...1.2...1.1

...2.2...2.2...1.3...1.3...1.4...2.3...1.3...1.2...3.1...1.4...1.3...1.2...1.1

...3.4...3.3...4.3...4.3...1.4...4.1...4.2...3.3...3.3...1.4...1.4...3.2...1.2

...4.4...3.4...4.4...4.3...2.4...4.4...4.4...4.4...3.3...3.4...2.4...3.4...3.4

CROSSREFS

Sequence in context: A052669 A076527 A247112 * A166797 A196453 A037594

Adjacent sequences:  A166812 A166813 A166814 * A166816 A166817 A166818

KEYWORD

nonn

AUTHOR

R. H. Hardin Oct 21 2009

STATUS

approved

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Last modified August 5 21:18 EDT 2020. Contains 336213 sequences. (Running on oeis4.)