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A337502 Minimum number of painted cells in an n X n grid to avoid unpainted tetrominoes. 2
0, 1, 3, 6, 9, 15, 20, 27, 34, 43 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

For n = 4, painting only 5 cells would leave an unpainted tetromino, but painting the following 6 cells avoids all unpainted tetrominoes:

. . X .

X X . X

. . X .

. X . .

CROSSREFS

Cf. A337501.

Sequence in context: A143981 A031940 A007187 * A082004 A112773 A070885

Adjacent sequences:  A337499 A337500 A337501 * A337503 A337504 A337505

KEYWORD

nonn,more

AUTHOR

Rob Pratt, Aug 29 2020

STATUS

approved

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Last modified February 27 05:37 EST 2021. Contains 341649 sequences. (Running on oeis4.)