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%I #9 Jan 23 2019 20:01:07
%S 0,2,13,284,13375,660690,51941832
%N Number of n-indecomposable polyominoes with at least 2n cells.
%C A polyomino is called n-indecomposable if it cannot be partitioned (along cell boundaries) into two or more polyominoes each with at least n cells.
%C For full lists of drawings of these polyominoes for n <= 6, see the links in A125759.
%H N. MacKinnon, <a href="http://www.jstor.org/stable/3618845">Some thoughts on polyomino tilings</a>, Math. Gaz., 74 (1990), 31-33.
%H Simone Rinaldi and D. G. Rogers, <a href="http://www.jstor.org/stable/27821767">Indecomposability: polyominoes and polyomino tilings</a>, The Mathematical Gazette 92.524 (2008): 193-204.
%e The five 2-indecomposable polyominoes:
%e ...................X.
%e XX..XXX..XX..XXX..XXX
%e ..........X...X....X.
%e Only the last two have >= 4 cells, so a(2) = 2.
%Y Row sums of A126743. Cf. A000105, A125759, A125761, A125709, A125753.
%K nonn,more
%O 1,2
%A _David Applegate_ and _N. J. A. Sloane_, Feb 01 2007
%E a(4) and a(5) from Peter Pleasants, Feb 13 2007
%E a(6) and a(7) from _David Applegate_, Feb 16 2007
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