

A269869


Number of matchings (not necessarily perfect) in the triangle graph of order n.


8



1, 4, 27, 425, 14278, 1054396, 169858667, 59811185171, 46012925161519, 77344464552678876, 284066030784415134855, 2279568155737623235728996, 39969481180418160836567285156, 1531253921482570179838977438893104, 128176575381689893022287259560629125869
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OFFSET

1,2


COMMENTS

The triangle graph of order n has n rows with i vertices in row i. Each vertex is connected to the neighbors in the same row and up to two vertices in each of the neighboring rows. The graph has A000217(n) vertices and 3*A000217(n1) edges altogether.


LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..25
Eric Weisstein's World of Mathematics, Independent Edge Set
Eric Weisstein's World of Mathematics, Matching
Eric Weisstein's World of Mathematics, Triangular Grid Graph


CROSSREFS

Cf. A000217, A028420, A039907, A112676, A178446.
Row sums of A288852.
Sequence in context: A271615 A271616 A123672 * A119030 A120093 A197987
Adjacent sequences: A269866 A269867 A269868 * A269870 A269871 A269872


KEYWORD

nonn


AUTHOR

Andrew Howroyd, Mar 06 2016


STATUS

approved



