[seqfan] Re: Bad pdf file in A002369?

Richard J. Mathar mathar at mpia-hd.mpg.de
Sat Feb 24 21:01:24 CET 2018


The construction of sequence A002369 is not clear to me either
(probably because I don't understand the fine-tuned French).
A056780 counts the shapes of polyominoes of rectangular cells, where 
polyominoes are considered equivalent if they can be
mapped onto each other by the symmetry group of the
rectangle of order 4 (unity, 180 degrees rotations, horizontal flip,
vertical flip). 
Devisme seems to say he has counted A002369 by counting a tree-structure
and by considering paths stepping across connected cells horizontally
or vertically.
So which shapes of A056780 are not counted in A002369 and why?

RJM


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