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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, 85, 96, 108, 121, 133, 146, 161, 176, 190, 208
OFFSET
0,4
COMMENTS
Inspired by the Japanese puzzle of the same name.
FORMULA
a(n) = A239072(n-4) + 2*n - 2 for n > 4.
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
KEYWORD
nonn,more
AUTHOR
Elliott Line, Mar 13 2014
EXTENSIONS
Some values corrected, incorrect values removed by Elliott Line, Aug 21 2014
a(16) and a(20) corrected by Elliott Line at the suggestion of Greg Malen, Sep 02 2020
STATUS
approved