

A071103


Number of perfect matchings in variant of n X n+2 Aztec rectangle graph.


0



12, 168, 4224, 206848, 20316160, 4053794816, 1651951796224, 1376451119022080, 2342575493674434560, 8125862822063095414784, 57307393009149041432330240
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OFFSET

1,1


COMMENTS

The graph consists of the vertices (x,y) bounded by 0<=x<=2n+1, 0<=y<=2n+1, n+1<=x+y<=3n+1 and yx<=n+2. Vertices (x1,y1) and (x2,y2) are adjacent iff x1x2=1 and y1=y2 or x1=x2 and y1y2=1 or x1x2=y1y2=1 and x1+y1+n is odd. The graph is planar, has A090288(n) vertices and 6*n^2 + 12*n + 1 edges. Figure 12 in the J. Propp reference shows the graph for n=3.  Andrew Howroyd, Mar 06 2016


REFERENCES

J. Propp, Enumeration of matchings: problems and progress, pp. 255291 in L. J. Billera et al., eds, New Perspectives in Algebraic Combinatorics, Cambridge, 1999 (see Problem 28).


LINKS

Table of n, a(n) for n=1..11.
J. Propp, Updated article
J. Propp, Enumeration of matchings: problems and progress, in L. J. Billera et al. (eds.), New Perspectives in Algebraic Combinatorics


CROSSREFS

Sequence in context: A282045 A304960 A113380 * A012489 A027772 A099270
Adjacent sequences: A071100 A071101 A071102 * A071104 A071105 A071106


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, May 28 2002


EXTENSIONS

a(4) inserted, a(6)a(11) from Andrew Howroyd, Mar 06 2016


STATUS

approved



