[seqfan] Figures built out of dominoes

[Neil Sloane]

Some really nice geometrical sequences!
Take n identical dominoes and make a connected figure in the plane.
How many ways?
Cesar Lozada recently studies a new version, where 2 long edges may not
meet, and the adjacency graph must be a tree.
You can also allow rotations and reflections, or not.
As a result we have 6 sequences:
A056786, A216598, A216583, A216595, A216492, A216581.
A216598, A216583, A216595 badly need more terms, and they all need checking.
Owen Whitby extended A056786 three years ago, so I am sending this to him
also.
Neil

-- 
Dear Friends, I have now retired from AT&T. New coordinates:

Neil J. A. Sloane, President, OEIS Foundation
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