

A125759


Number of nindecomposable polyominoes.


7




OFFSET

1,2


COMMENTS

A polyomino is called nindecomposable if it cannot be partitioned (along cell boundaries) into two or more polyominoes each with at least n cells.
MacKinnon incorrectly implies that the sequence is 1,6,44.
MacKinnon only allows polyominoes with >= n cells, leading to A125709 and A125753.
The polyominoes with < 2n cells are uninteresting, leading to A126742 and A126743.
There is a sense in which ndecomposable polyominoes with >3n2 cells are also uninteresting: they are precisely the "nspiders", where an nspider is a polyomino with a cell whose removal splits it into 4 components each with <n cells.  Peter Pleasants, Feb 18 2007


LINKS



FORMULA



EXAMPLE

The six 2indecomposable polyominoes:
......................X.
X..XX..XXX..XX..XXX..XXX
.............X...X....X.


CROSSREFS



KEYWORD

nonn,more


AUTHOR



EXTENSIONS

a(4) and a(5) from Peter Pleasants, Feb 13 2007


STATUS

approved



