A071106 Number of perfect matchings in variant of right triangle graph with n edges where n runs through numbers congruent to 0 or 3 mod 4.

1, 3, 6, 1065, 6276, 45949563, 807343128, 221797080594801, 11812299253803024, 117066491250943949567763, 19100803250397148607852640, 6685924427990669481186818442889689, 3366736732994780307970181864980219968

Offset

0,2

Comments

See A071105 for a description of the graph. - Andrew Howroyd, Mar 06 2016

References

J. Propp, Enumeration of matchings: problems and progress, pp. 255-291 in L. J. Billera et al., eds, New Perspectives in Algebraic Combinatorics, Cambridge, 1999 (see Problem 29).

Links

Table of n, a(n) for n=0..12.

J. Propp, Updated article

J. Propp, Enumeration of matchings: problems and progress, in L. J. Billera et al. (eds.), New Perspectives in Algebraic Combinatorics

Formula

a(2n) = A071105(4n), a(2n+1) = A071105(4n+3). - Andrew Howroyd, Mar 06 2016

Mathematica

A071105 = Cases[Import["https://oeis.org/A071105/b071105.txt", "Table"], {_, _}][[All, 2]];
a[n_] := A071105[[(4n+3-(-1)^n)/2]];
a /@ Range[0, 12] (* Jean-François Alcover, Sep 06 2019 *)

Crossrefs

Cf. A071105.

Sequence in context: A308259 A034879 A113588 * A157548 A134901 A157564

Adjacent sequences: A071103 A071104 A071105 * A071107 A071108 A071109

Keyword

nonn

Author

N. J. A. Sloane, May 28 2002

Extensions

Propp gives 2 more terms.

a(9)-a(12) from Andrew Howroyd, Mar 06 2016

Status

approved