OFFSET
0,2
REFERENCES
Per Hakan Lundow, "Computation of matching polynomials and the number of 1-factors in polygraphs", Research report, No 12, 1996, Department of Math., Umea University, Sweden.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..900
Per Hakan Lundow, Enumeration of matchings in polygraphs, 1998.
FORMULA
G.f.: -(x^7-5*x^6 -21*x^5 +41*x^4 +41*x^3 -21*x^2 -5*x +1) / (x^9 -7*x^8 -56*x^7 +104*x^6 +280*x^5 -280*x^4 -104*x^3 +56*x^2 +7*x -1). - Alois P. Heinz, Dec 09 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved