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A239231 Heyawake numbers: maximum number of painted cells in an n X n grid, such that no two painted cells are orthogonally adjacent and the unpainted cells form a contiguous area. 2
0, 1, 1, 4, 5, 9, 12, 17, 21, 27, 33, 41, 48, 56, 65, 75, 84, 96, 108, 121, 132, 146, 161, 176, 190, 208 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Inspired by the Japanese puzzle of the same name.

LINKS

Table of n, a(n) for n = 0..25

Wikipedia, Heyawake

FORMULA

If n>4, a(n) = A239072(n-4)+2n-2.

EXAMPLE

For example, if n=6, the painted cells could be A1, A3, A6, B5, C1, C3, D4, D6, E2, F1, F4, F6 (12 cells in all).

CROSSREFS

Cf. A239072 (makes up the inner n-4 X n-4 square of the grid).

Sequence in context: A200535 A010405 A125603 * A078507 A060199 A229240

Adjacent sequences:  A239228 A239229 A239230 * A239232 A239233 A239234

KEYWORD

nonn,more

AUTHOR

Elliott Line, Mar 13 2014

EXTENSIONS

Some values corrected, incorrect values removed by Elliott Line, Aug 21 2014

STATUS

approved

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Last modified May 25 22:17 EDT 2019. Contains 323576 sequences. (Running on oeis4.)