A028456 Number of perfect matchings in graph P_{2} X C_{4} X P_{n}.

1, 9, 272, 6345, 155969, 3794880, 92524801, 2254970505, 54961579408, 1339585632201, 32649998822849, 795784687676160, 19395815427419969, 472737980834179401, 11522134787497383568, 280831232750814806025, 6844754271574955786881, 166828527501840135007680

Offset

0,2

Links

Alois P. Heinz, Table of n, a(n) for n = 0..500

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.

Per Hakan Lundow, Enumeration of matchings in polygraphs, 1998.

Formula

G.f.: -(1+x)*(x^4-16*x^3+45*x^2-16*x+1) / ( (x-1)*(x^6-23*x^5-50*x^4+405*x^3-50*x^2-23*x+1) ). - R. J. Mathar, Dec 13 2013

Crossrefs

Sequence in context: A218693 A258302 A336195 * A180358 A220866 A197597

Adjacent sequences: A028453 A028454 A028455 * A028457 A028458 A028459

Keyword

nonn

Author

Per H. Lundow

Status

approved