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%I #14 Aug 30 2020 17:58:08
%S 0,0,3,5,8,13,17,24,31,39
%N Minimum number of painted cells in an n X n grid to avoid unpainted pentominoes.
%H Puzzling Stack Exchange, <a href="https://puzzling.stackexchange.com/questions/101485/least-amount-of-marked-symbols">Least number of marked symbols</a>
%e For n = 3, painting only 2 cells would leave an unpainted pentomino, but painting the following 3 cells avoids all unpainted pentominoes:
%e . . .
%e . X X
%e X . .
%Y Cf. A337501, A337502.
%K nonn,more
%O 1,3
%A _Rob Pratt_, Aug 29 2020