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Square sequence (Posted on 2003-09-09) Difficulty: 3 of 5
Here is a square sequence of numbers.

392?
6  3
7  4
?817
What are the two question marks?

See The Solution Submitted by Gamer    
Rating: 4.5000 (4 votes)

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Some Thoughts re(3): Solution (further analysis) | Comment 12 of 18 |
(In reply to re(2): Solution by SilverKnight)

And in Gamer's vein, let's take a look at his observation and see what we find...

Note that... you can start with any two digit number (from 00-99), and generate one of these patterns. It *will* cycle (eventually). Here are the cycles:

Period 1:
0

Period 3:
550
550 (can't divide the period in half, showing it a 2nd time)

Period 4:
26
84

Period 12:
392134
718976

Period 20:
4606628088
6404482022

Period 60:
325729101123583145943707741561
785381909987527965167303369549
________

  • The sequence that corresponds to the puzzle has period 12, but this puzzle could have easily used one of these other sequences
  • Note that I split each one in half lining up opposing numbers (to demonstrate that opposing numbers all add up to 10)
  • Also note that the period = the number of digits in the string = the number of two digit combinations that exist in that sequence... therefore,
  • If you sum the periods of each sequence, they add up to 100. 1 + 3 + 4 + 12 + 20 + 60 = 100 (If you don't like 00, then just include (01-99) and eliminate the sequence with period 1.) and
  • This makes sense since each number (00-99) will generate the whole sequence to which it belongs (e.g., if I start with 63, or 39, or 92, or 47, I will generate the sequence with Period 12). Each two digit number can generate one and only one sequence. And all two digit numbers will generate a sequence.
    ____________

    Okay enough analysis on this puzzle for a while... who's taking it from here?

      Posted by SilverKnight on 2003-09-09 23:25:45
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