by Yogi » Fri Oct 28, 2022 10:42 am
A possible explanation could be that the intention was to produce a list of valid 17-clue sudoku puzzle codes, assembled numerically in canonical form. This would mean that the list would only include codes which solve to a single unique solution, and would probably start with those puzzles with clues something like 00000100200... followed by 00000102... and so-on. Only after exhausting all possibilities starting with five or more zeros then 1, would it move on to 000002.. and later to 000003
After moving on to codes starting with 000009 the list would only then move on to those with 00001..
Remember also that 0 is not a number. It just represents an unfilled cell in the initial code string.
In some systems they use . instead of 0 to avoid the implication that 0 is a number.
This approach makes it appear (falsely) that there are far more codes with empty top left cells. Another factor which could skew the picture is that a definitive list would not include codes which represent the same puzzles which have been included earlier in the list, but have a different number set. After all, the characters we use in sudoku puzzles are not numbers with numerical values, only symbols, which can be freely interchanged.