### SuJoku FAQ (Frequently Asked Questions)

Q:"What does the Solution String '22ip - 2087 - 1' mean?"
I see it on the bottom of your Sudoku Puzzles and would like to know what it refers to..."

Refer to Desmond Puzzle #376

A: The Solution String series of 3 #s refers to the following:

- 1. '22ip' - there are 22 Input Numbers in the Puzzle (NB: a complete Puzzle has 81 #s in the 9x9 Block);
- 2. '2087' - this is the # of iterations that it took our proprietary C Computer Program to calculate a unique (single) solution to the Puzzle... Why does it have to be unique? If it didn't have only ONE unique solution, you'd go crazy trying to figure out why your answer didn't match our solution! (i.e. Have a look at the "World's Largest Sudoku Puzzle" where there are 1905 Solutions!). OK, so the number 2087 doesn't mean anything to you - BUT it does give a good indication to the level of difficulty of the Puzzle (i.e. Kids Puzzle #390 has a Solution String of 72ip - 8 - 9 whereas the much more challenging Puzzle #342 has a Solution String of 17ip - 12487350 - 1); and
- 3. '1' - this means that there is one empty cell within the Puzzle that has only ONE # that is possible. How? Look at the rows, column, and 3x3 blocks related to that cell and you'll see that 8 of the 9 #s are already shown as Input Numbers... Refer to Desmond Puzzle #376 - Possible Cell #s From the above pdf file, you can see that the ONLY cell which has only ONE possible solution # is for the cell in the 1st row, 4th column - it MUST be a #9 - as follows: Row Analysis: Row 1 has #s 7, 1, 2 & 4 Column Analysis: Column 4 has #s 8, 6 & 5 Top Middle 3x3 Block Analysis: has #s 8, 7 & 3 The ONLY # missing in that Cell is #9!

Q:"What is a 'Sierpinski' puzzle?"

A: The term 'Sierpinski' refers to a group of dedicated mathematicians in the world who are trying to determine "What is the smallest Sierpinski number?" (refer to www.SeventeenOrBust.com) Executive Summary: The "Sierpinski Problem" deals with numbers of the form N = k * 2^n + 1, for any odd k and n > 1 (... you may need to brush up on prime & composite numbers ...) In 1962, John Selfridge found what was thought to be the smallest Sierpinski number (78557). Since then, mathematicians have been trying to prove that it is the smallest by a process of elimination. When the "Seventeen Or Bust" group started (March 2002), there were only 17 uncertain prime numbers smaller than 78557 (values of k) to check: k = 4847, 5359, 10223, 19249, 21181, 22699, 24737, 27653, 28433, 33661, 44131, 46157, 54767, 55459, 65567, 67607 & 69109. To disprove these numbers, they setup a public distributed-computing project, with volunteer's computer muscle power churning out calculations (~ 1800 participants in 2003). Since its inception, the group has eliminated 7 of the above 17 #s (as of Feb 2006), with 10 more to go... In honour of the tremendous dedication of this group of mathematicians to test 17 #s, we at joe-ks.com dedicate our 17 IP # Sudoku Puzzles to this group - to Sudoku Puzzles which have exactly 17 Input #s...

Q: "What are your toughest puzzles?" "Why do Sudoku Puzzles have to have a minimum of 17 Input #s, and why is a Puzzle with 17 Input #s considered the toughest of all Sudoku Puzzles?"

A: As of 2007, no one in the world has created a Sudoku Puzzle that contains fewer than 17 numbers and has a single solution. Are those the toughest of all Sudoku Puzzles to solve? That totally depends on the person who is trying to solve the Puzzle! We're still amazed to find out that a few of our subscribers solve our Sierpinski Puzzles in 30 to 40 minutes, when it takes some 'puzzle-challenged' people more than 4 hours to do the same Puzzles! A beginner assumes that there is a direct correlation between the amount of Input #s and the level of difficulty in solving a Sudoku Puzzle. While it's true that solving a Sudoku Puzzle with 80 Input #s (Redneck Sudoku) is much easier than solving a Sudoku Puzzle with only 17 Input #s (Sierpinski Sudoku), there is NO direct correlation between the # of Input #s and how tough a Sudoku puzzle is. The difference, for example, between a Medium and Fiendish puzzle is much more than comparing Input #s (or Given #s). The difficulty is related to: (A) the placement of the Given #s in a puzzle, and (B) the levels and complexity of techniques required to solve a puzzle. A beginner would have great difficulty solving a puzzle that required knowledge of Possibility Matrixes, Hidden Pairs or X-Wings! A true Sudokuholic utilizes a mixture of simple and advanced techniques to solve the most difficult puzzles. PS: If you know of anyone who has created a Sudoku Puzzle with < 17 Input #s (& it solves with a unique solution), let us know - and we'll reward both of you!

Q:What is a 'Synchronized' Sudoku Puzzle?"

A: All numbers in our Sudoku Puzzles are arranged in a symmetrical pattern. To achieve a symmetrical puzzle, the puzzle must be hand-crafted, and NOT computer generated. The only exception to this are our Sierpinski Puzzles - since they have only 17 Input #s (and the only reason for making them is to make them the toughest, with no respect to synchronism).