OFFSET
1,3
COMMENTS
Also the number of polyplets (A030222) on n points up to isomorphism of adjacency graphs.
LINKS
P. C. Staecker, Some enumerations of binary digital images, arXiv 1502.06236 [math.CO], 2015 (see table p. 6).
P. C. Staecker, Digital image enumerations
EXAMPLE
For n=4 the a(4)=6 images are:
X X X X XX X X
X X X X XX XX XX
X X X X X
X
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
P. Christopher Staecker, Feb 24 2015
STATUS
approved