“PseuDoKu” = What I’m calling variants of sudoku, whether simplificiation of or extrapolation from the original.

My daughter enjoys playing the “number game” on my phone with me; I tell her where to put the next solved number (“put a 2 between the 5 and the 6 in that grey box”, etc.). I’ve thus started doing simpler grids on the chalkboard — with just a 4×4 grid, and one number missing from each row or column, and haven’t made the logic require one-of-each-per-2×2. The other day, she asked for “1 to 5” instead of “1 to 4”: since I haven’t introduced her to the boxes, the fact that 5×5 cannot have the sub-box regions is irrelevant.

But the 4×4 got me thinking: just how many valid solutions of 4×4 are there? 288 (that’s just two gross). If you care about the details, see my highly mathematical “PseuDoKu Details” article.

Otherwise, reload the page to see a different board.

For playable kids’ sudoku, see 1sudoku.net’s 4×4 and 6×6. If you’d rather avoid the ads on 1sudoku.net, try out sudoku-download.net, which has PDF’s of 4×4 thru 25×25 (and even example 49×49 and 64×64!)