OFFSET
0,3
COMMENTS
See A107739 for definition of an n^2 X n^2 sudoku.
a(2) = 2 independently computed by Gary McGuire and Hugo van der Sanden.
For the 9 X 9 case the allowed equivalences are (see link to Jarvis et al.):
- relabeling entries; reflection; rotation;
- permutation of blocks of columns 1-3, 4-6 and 7-9;
- permutation of blocks of rows 1-3, 4-6 and 7-9;
- permutation of columns 1-3; permutation of rows 1-3;
- permutation of columns 4-6; permutation of rows 4-6;
- permutation of columns 7-9; permutation of rows 7-9.
See A107739 for the total number of ("square") sudoku grids, A114288 for the lexicographically earliest 9 X 9 solution. - M. F. Hasler, Mar 29 2013
REFERENCES
J.-P. Delahaye, "Le tsunami du Sudoku" in 'Pour La Science' (French Edition of "Scientific American"), December 2005 pp. 144-9, Paris.
LINKS
J. P. Grossman, Javascript Sudoku solver
S. Gupta, Exploring the Mathematics of Su Doku
Frazer Jarvis et al., Sudoku enumeration problems
Eric Weisstein's World of Mathematics, Sudoku
Wikipedia, Sudoku
EXAMPLE
a(2) = 2:
12|34 12|34
34|12 34|12
--+-- --+--
21|43 23|41
43|21 41|23
CROSSREFS
KEYWORD
nonn,bref,hard
AUTHOR
N. J. A. Sloane, Aug 13 2005
EXTENSIONS
Links to Jarvis et al. fixed by M. F. Hasler, Mar 29 2013
STATUS
approved