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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
OFFSET
1,2
LINKS
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
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...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 A343091
KEYWORD
nonn
AUTHOR
R. H. Hardin Oct 21 2009
STATUS
approved