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 A166758 Number of nX2 1..5 arrays containing at least one of each value, and all equal values connected. 1
 0, 0, 840, 13320, 99720, 495720, 1889760, 5967360, 16358640, 40158000, 90215640, 188431320, 370311480, 691081560, 1233676080, 2118959760, 3518563680, 5670751200, 8899759080, 13639089960, 20459263080, 30100560840, 43511339520 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS R. H. Hardin, Table of n, a(n) for n=1..28 FORMULA Empirical: a(n) = (1/21)*(n-1)*(n-2)*(16*n^6 - 80*n^5 + 512*n^4 - 1720*n^3 + 3525*n^2 - 4227*n + 2520). From G. C. Greubel, May 26 2016: (Start) Empirical G.f.: 120*x^3*(2*x^6 + 12*x^5 + 43*x^4 + 60*x^3 + 84*x^2 +48*x + 7 ) / (1-x)^9. Empirical E.g.f.: (1/21)*(5040 - 5040*x + 2520*x^2 + 2100*x^3 + 8925*x^4 + 7224*x^5 + 2352*x^6 + 320*x^7 + 16*x^8)*exp(x) - 240. (End) EXAMPLE Some solutions for n=3 ...4.3...4.5...1.1...2.3...2.2...4.3...1.1...2.5...1.3...5.3...3.4...4.5...5.4 ...1.5...4.2...5.2...1.3...5.4...5.1...2.4...3.3...4.5...4.1...5.1...1.1...1.1 ...1.2...1.3...3.4...5.4...1.3...2.2...3.5...1.4...2.2...2.1...5.2...2.3...2.3 ------ ...1.2...1.4...1.5...3.5...4.1...1.2...1.2...4.1...1.2...5.5...3.1...1.3...5.1 ...3.4...1.2...4.4...2.4...3.5...5.2...3.4...2.3...3.5...2.3...3.2...4.4...4.2 ...5.4...5.3...2.3...2.1...2.2...3.4...3.5...5.5...4.5...1.4...5.4...5.2...3.3 CROSSREFS Sequence in context: A135038 A215230 A171260 * A188781 A166764 A226268 Adjacent sequences: A166755 A166756 A166757 * A166759 A166760 A166761 KEYWORD nonn AUTHOR R. H. Hardin, Oct 21 2009 STATUS approved

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Last modified December 4 23:46 EST 2022. Contains 358572 sequences. (Running on oeis4.)