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 + 90*n^3 - 746*n^2 + 702*n - 180) /180.
From G. C. Greubel, May 26 2016: (Start)
Empirical G.f.: -x^2*(x^5 + 2*x^4 - 20*x^3 + 32*x^2 - 11*x - 8)/(1-x)^7.
Empirical E.g.f.: (1/180)*(-180 + 180*x + 630*x^2 + 1320*x^3 + 360*x^4 + 33*x^5 + x^6)*exp(x) + 1. (End)
EXAMPLE
Some solutions for n=4
...1.4...1.2...1.4...1.2...1.2...1.4...1.4...2.3...1.3...1.1...1.2...1.2...1.1
...1.4...3.3...1.4...2.2...2.2...2.4...1.4...3.3...1.3...1.4...3.2...1.2...1.2
...3.2...3.3...2.2...2.2...3.2...3.3...2.3...3.3...2.2...2.2...4.4...3.3...1.2
...3.2...3.4...2.3...3.4...4.4...3.3...3.3...4.1...2.4...3.3...4.4...4.4...3.4
------
...1.2...1.2...1.2...1.4...1.2...1.1...1.3...1.3...1.3...1.4...1.2...1.2...1.3
...3.2...3.3...1.3...2.2...3.3...1.4...2.2...1.3...2.3...2.4...3.2...3.2...2.4
...4.2...4.3...3.3...3.2...4.4...3.2...2.4...1.3...3.3...2.4...3.3...4.2...2.4
...4.4...4.3...4.4...3.2...4.4...3.3...4.4...4.2...4.4...3.3...4.4...4.2...4.4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 21 2009
STATUS
approved