Sudoku enumeration problems

There are 6670903752021072936960 Sudoku grids (Bertram Felgenhauer and Frazer Jarvis)

See

• Details of the enumeration
• A summary page of results from Ed Russell's program
• Original write-up
• Recent rewrite

It seems that we were not, after all, the first to compute this number: see the contribution from “QSCGZ” to rec.puzzles in Sepember 2003 (spotted by Ed Russell, February 1st 2008).

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

See

• Calculations with the group of symmetries of a Sudoku grid
• Write-up of this calculation

There are 49 essentially different 2x3 Sudoku grids (Ed Russell and Frazer Jarvis)

(Note that the terminology refers to 6x6 grids divided into 2x3 boxes.) See these calculations with the group of symmetries of a 2x3 Sudoku grid.

There are 1673187 essentially different Sudoku 2x4 grids (Ed Russell)

(Note that the terminology refers to 8x8 grids divided into 2x4 boxes in the obvious way.) See these calculations with the group of symmetries of a 2x4 Sudoku grid.

There are 4743933602050718 essentially different Sudoku 2x5 grids (Kjell Fredrik Pettersen)

(10x10 grids divided into 2x5 boxes in the obvious way.) See these calculations with the group of symmetries of a 2x4 Sudoku grid.

Frazer Jarvis, February 2nd 2008. Home page.