

A126742


Number of nindecomposable polyominoes with at least 2n cells.


5




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.
For full lists of drawings of these polyominoes for n <= 6, see the links in A125759.


LINKS

Table of n, a(n) for n=1..7.
N. MacKinnon, Some thoughts on polyomino tilings, Math. Gaz., 74 (1990), 3133.
Simone Rinaldi and D. G. Rogers, Indecomposability: polyominoes and polyomino tilings, The Mathematical Gazette 92.524 (2008): 193204.


EXAMPLE

The five 2indecomposable polyominoes:
...................X.
XX..XXX..XX..XXX..XXX
..........X...X....X.
Only the last two have >= 4 cells, so a(2) = 2.


CROSSREFS

Row sums of A126743. Cf. A000105, A125759, A125761, A125709, A125753.
Sequence in context: A086510 A326360 A123113 * A013051 A012955 A011808
Adjacent sequences: A126739 A126740 A126741 * A126743 A126744 A126745


KEYWORD

nonn,more


AUTHOR

David Applegate and N. J. A. Sloane, Feb 01 2007


EXTENSIONS

a(4) and a(5) from Peter Pleasants, Feb 13 2007
a(6) and a(7) from David Applegate, Feb 16 2007


STATUS

approved



