0,3

See A107739 for definition of a sudoku.

a(2) = 2 independently computed by Gary McGuire and Hugo van der Sanden.

For the 9 X 9 case the allowed equivalences are: 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.

J.-P. Delahaye, "Le tsunami du Sudoku" in 'Pour La Science' (French Edition of "Scientific American"), December 2005 pp. 144-9, Paris.

Bertram Felgenhauer and Frazer Jarvis, There are 6670903752021072936960 Sudoku grids

J. P. Grossman, Javascript Sudoku solver

S. Gupta, Exploring the Mathematics of Su Doku

Ed Russell and Frazer Jarvis, There are 5472730538 essentially different Sudoku grids

Wikipedia, Sudoku

Eric Weisstein's World of Mathematics, Sudoku

a(2) = 2:

12|34 12|34

34|12 34|12

--+-- --+--

21|43 23|41

43|21 41|23

Sequence in context: A034251 A051241 A094486 this_sequence A105759 A154422 A154423

Adjacent sequences: A109738 A109739 A109740 this_sequence A109742 A109743 A109744

nonn

N. J. A. Sloane (njas(AT)research.att.com), Aug 13 2005