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%I #9 Aug 30 2020 03:04:38
%S 0,2,4,8,11,18,23,32,39,50
%N Minimum number of painted cells in an n X n grid to avoid unpainted trominoes.
%e For n = 3, painting only 3 cells would leave an unpainted tromino, but painting the following 4 cells avoids all unpainted trominoes:
%e . . X
%e X X .
%e . . X
%K nonn,more
%O 1,2
%A _Rob Pratt_, Aug 29 2020
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