Last year we talked about Sudoku (Great new way to waste time catches on fast), and followed that up with a blog about Kakuro (Do you do or do you don't 'doku?). There, we said that: “We at Dewey Manor don't think Sudoku really counts as a mathematical game, since it doesn't require players to carry out any mathematical operations,” and “[Kakuro] is really a test of logic, not of arithmetic.” So we assigned Sudoku and Kakuro the Dewey number 793.73 Puzzles and puzzle games, and not 793.74 Mathematical games and recreations.
However, in the comments on the first blog, Thom Hickey and Dennis McGovern disagreed with us. Dennis (writing under the handle of “LCDennis”) said:
I disagree with the other residents of Dewey Manor in that I think Sudoku really counts as a mathematical game, even though it doesn't require players to carry out any mathematical operations. The popular version of Sudoku (i.e., the one described in the 1st 20 Google results) is played using numbers (mathematical symbols). I think of number games as mathematical recreations, and I agree with the LC subject heading (sh85082131) which has Number games as a 450 ref. to Mathematical recreations. To my way of thinking Guardian's Godoku (which doesn't have much literary warrant) is another game: a logical game using letters that should also class in 793.74.
These things have way of coming back to bite you, and we have just dealt with assigning Dewey numbers to the LCSH Weekly List containing “Sudoku.” (Weekly List 2005 no. 37 -- the list with “Kakuro” is still in our future). And we’ve had a change of heart: we’ve decided that Sudoku is a game involving Latin squares, a topic within 511.64 Permutations and combinations, while Kakuro involves 519.77 Integer programming. The Wikipedia even has an article on the Mathematics of Sudoku.
510 Mathematics is a large topic, and now includes a lot more than traditional topics like algebra, calculus, geometry and statistics: it includes many other formalized and axiomatised systems, such as 511.3 Mathematical logic, 511.6 Combinatorics, and 519.7 Programming (which is not the same topic as the mathematics of computer programming, but includes linear programming and nonlinear programming). Both Sudoku and Kakuro fit within this broader concept of mathematics, and belong in 793.74 Mathematical games and recreations.