A166760 Number of nX2 1..7 arrays containing at least one of each value, and all equal values connected.

0, 0, 0, 50400, 1380960, 16803360, 129764880, 740028240, 3386113920, 13088718720, 44246270880, 134067769920, 370807123680, 949269877920

Offset

1,4

Links

Table of n, a(n) for n=1..14.

Formula

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

Empirical a(n) = (1/1485)*(n-1)*(n-2)*(n-3)*(64*n^9 - 768*n^8 + 9648*n^7 - 73200*n^6 + 407526*n^5 - 1667892*n^4 + 4855097*n^3 - 9499725*n^2 + 11240730*n - 6237000).

Empirical G.f.: 5040*x^4*(5*x^9 + 44*x^8 + 187*x^7 + 452*x^6 + 827*x^5 + 958*x^4 + 917*x^3 + 552*x^2 + 144*x + 10)/(1-x)^13.

Empirical E.g.f.: (1/1485)*(37422000 - 37422000*x + 18711000*x^2 - 6237000*x^3 + 4677750*x^4 + 13659030*x^5 + 19178775*x^6 + 11594880*x^7 + 3632310*x^8 + 628320*x^9 + 60720*x^10 + 3072*x^11 + 64*x^12)*exp(x) - 25200. (End)

Example

Some solutions for n=4
...4.5...7.6...4.2...4.2...5.3...5.3...2.2...6.1...7.4...7.5...7.5...2.4...4.5
...3.6...1.1...1.6...1.3...2.4...4.1...5.4...7.1...3.2...4.1...4.2...2.7...4.7
...3.2...2.5...5.7...5.5...2.1...7.7...1.7...3.5...6.2...2.6...3.6...5.6...6.2
...7.1...3.4...5.3...7.6...6.7...2.6...3.6...4.2...5.1...2.3...1.6...3.1...3.1
------
...1.7...1.6...4.1...4.3...3.1...2.3...6.3...5.5...2.3...5.7...2.7...1.5...2.1
...3.2...2.2...3.2...5.1...7.2...5.5...7.1...7.1...1.7...3.4...2.4...2.6...4.4
...6.4...7.3...5.6...7.7...5.2...4.7...7.4...4.2...1.4...3.1...6.1...3.7...5.3
...6.5...5.4...7.6...2.6...4.6...6.1...2.5...3.6...5.6...2.6...3.5...3.4...6.7

Crossrefs

Sequence in context: A237949 A251466 A267252 * A231918 A029823 A302902

Adjacent sequences: A166757 A166758 A166759 * A166761 A166762 A166763

Keyword

nonn

Author

R. H. Hardin, Oct 21 2009

Status

approved