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A198297 Minimum number of clues needed to uniquely solve an n^2 X n^2 sudoku. 1
0, 0, 4, 17 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

McGuire, Tugemann, & Civario find a(3) = 17.

LINKS

Table of n, a(n) for n=0..3.

Gary McGuire, Bastian Tugemann, and Gilles Civario, There is no 16-clue sudoku: solving the sudoku minimum number of clues problem (2012)

James Grime and Brady Haran, 17 and sudoku clues, Numberphile video (2012)

EXAMPLE

Every 4x4 board with 3 filled squares either cannot be completed, or can be completed in two or more ways. But with 4 filled squares it is possible:

+--+--+

| 1|2 |

|  |  |

+--+--+

|  |1 |

|  | 3|

+--+--+

Thus a(2) = 4.

CROSSREFS

Cf. A107739.

Sequence in context: A300315 A296628 A123234 * A317094 A116573 A195881

Adjacent sequences:  A198294 A198295 A198296 * A198298 A198299 A198300

KEYWORD

nonn,hard,bref

AUTHOR

Charles R Greathouse IV, Jan 26 2012

STATUS

approved

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Last modified January 22 11:34 EST 2019. Contains 319363 sequences. (Running on oeis4.)