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The New Coffee Room

  1. TNCR
  2. General Discussion
  3. Puzzle time - the Fibonacci numbers

Puzzle time - the Fibonacci numbers

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  • Doctor PhibesD Offline
    Doctor PhibesD Offline
    Doctor Phibes
    wrote on last edited by
    #18

    Are you two about to have a 'my dick is smaller' contest?

    I was only joking

    KlausK 1 Reply Last reply
    • Doctor PhibesD Doctor Phibes

      Are you two about to have a 'my dick is smaller' contest?

      KlausK Offline
      KlausK Offline
      Klaus
      wrote on last edited by
      #19

      @Doctor-Phibes Did you know that dick sizes have a Fibonacci distribution? It's a distribution with a very long tail...

      <insert @George-K rimshot image macro here>

      1 Reply Last reply
      • jon-nycJ jon-nyc

        Interesting observation:

        Cycle lengths 2^n = 3*2^(n-1) at least within the first 100. Does that continue?

        jon-nycJ Online
        jon-nycJ Online
        jon-nyc
        wrote on last edited by
        #20

        @jon-nyc said in Puzzle time - the Fibonacci numbers:

        Interesting observation:

        Cycle lengths 2^n = 3*2^(n-1) at least within the first 100. Does that continue?

        bump for Klaus and his little 4 line program.

        Only non-witches get due process.

        • Cotton Mather, Salem Massachusetts, 1692
        KlausK 1 Reply Last reply
        • jon-nycJ jon-nyc

          @jon-nyc said in Puzzle time - the Fibonacci numbers:

          Interesting observation:

          Cycle lengths 2^n = 3*2^(n-1) at least within the first 100. Does that continue?

          bump for Klaus and his little 4 line program.

          KlausK Offline
          KlausK Offline
          Klaus
          wrote on last edited by Klaus
          #21

          @jon-nyc said in Puzzle time - the Fibonacci numbers:

          @jon-nyc said in Puzzle time - the Fibonacci numbers:

          Interesting observation:

          Cycle lengths 2^n = 3*2^(n-1) at least within the first 100. Does that continue?

          bump for Klaus and his little 4 line program.

          Can you explain? You mean that the cycle length of Fib mod (2^n) is the same as Fib mod (3*2^(n-1))? That doesn't seem to be true.

          I uploaded the first 10,000 cycle lengths here, if you want to check this yourself.
          https://www.heypasteit.com/clip/0IV18W

          1 Reply Last reply
          • jon-nycJ Online
            jon-nycJ Online
            jon-nyc
            wrote on last edited by jon-nyc
            #22

            No, the cycle length of Fib mod (2^n) = 3*2^(n-1))

            Check Fmod2, Fmod4, Fmod8, Fmod16 etc for their cycle lengths. You’ll get 3,6,12,24,48 etc. I’m wondering if it holds. I think it will.

            Only non-witches get due process.

            • Cotton Mather, Salem Massachusetts, 1692
            1 Reply Last reply
            • KlausK Offline
              KlausK Offline
              Klaus
              wrote on last edited by
              #23

              Here's a list of pairs where the first number shows the "n" (but only for powers of 2) and the second one the associated cycle length. Maybe I missunderstood something but your conjecture doesn't seem to hold.

              [(2,6),(4,24),(8,60),(16,24),(32,36),(64,120),(128,420),(256,264),(512,516),(1024,72),(2048,600),(4096,1368),(8192,720)]
              
              1 Reply Last reply
              • jon-nycJ Online
                jon-nycJ Online
                jon-nyc
                wrote on last edited by jon-nyc
                #24

                But your original list is this one:

                (left side numbering mine, right side list yours)

                3e9774ed-e059-4cd4-956f-c8646a08d27b-image.png

                Only non-witches get due process.

                • Cotton Mather, Salem Massachusetts, 1692
                1 Reply Last reply
                • KlausK Offline
                  KlausK Offline
                  Klaus
                  wrote on last edited by
                  #25

                  Ah, looks like an "off by two" error somewhere. Hmm....

                  1 Reply Last reply
                  • KlausK Offline
                    KlausK Offline
                    Klaus
                    wrote on last edited by Klaus
                    #26

                    Turned out to be two "off by 1" errors that have to do with indices starting at 0 and not 1.

                    What about this result?

                    [(2,3),(4,6),(8,12),(16,24),(32,48),(64,96),(128,192),(256,384),(512,768),(1024,1536),(2048,3072),(4096,6144),(8192,12288)]
                    
                    1 Reply Last reply
                    • KlausK Offline
                      KlausK Offline
                      Klaus
                      wrote on last edited by Klaus
                      #27

                      It looks like linear relations between the cycle length happen quite frequently. This is a scatter plot of the cycle lengths I computed above (haven't used R in a while - fun for plotting data!). Observe all the dotted lines. The points you identified are on one of those lines. Also interesting to see a few outliers.

                      440d6f5b-c0a6-4d2d-b301-7d3d66c1fafd-image.png

                      I have marked the points you are interested in in red. You see that there are way more points on that line.

                      1 Reply Last reply
                      • jon-nycJ Online
                        jon-nycJ Online
                        jon-nyc
                        wrote on last edited by
                        #28

                        Interesting.

                        So it turns out Fibonacci cycle lengths a thing people study. They’re called Pisano numbers and understanding them is really about understanding Pisano numbers for prime powers.

                        A neat property is that if n and m are coprime then period(mn) is least common multiple of period(n) and period(m).

                        Only non-witches get due process.

                        • Cotton Mather, Salem Massachusetts, 1692
                        1 Reply Last reply
                        • jon-nycJ Online
                          jon-nycJ Online
                          jon-nyc
                          wrote on last edited by
                          #29

                          Wait a minute, is that really your graph up there? This is from Wiki

                          396851CA-71EE-4E8B-AB14-42964B4121AC.png

                          Only non-witches get due process.

                          • Cotton Mather, Salem Massachusetts, 1692
                          1 Reply Last reply
                          • KlausK Offline
                            KlausK Offline
                            Klaus
                            wrote on last edited by Klaus
                            #30

                            Yes, it's my graph. I haven't seen the WIki graph yet, but it shows the same data, so of course it's similar. It's an interesting coincidence that they also cut off at 10,000.

                            1 Reply Last reply
                            • KlausK Offline
                              KlausK Offline
                              Klaus
                              wrote on last edited by
                              #31

                              Just for fun, here's the continuation of the dataset for cycle lengths up to 20000.

                              1549ea7c-ea85-4eca-aea0-3b73c980f9aa-image.png

                              1 Reply Last reply
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