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Re: Counting digit in other base

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  • kraDen
    ... Expletive! I ve been running a pfgw script to answer David s question using the above 2^42643801-1 for the past 24 hours. I just noticed I should instead
    Message 1 of 47 , Nov 9, 2010
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      --- In primenumbers@yahoogroups.com, Alan Eliasen <eliasen@...> wrote:
      >
      > On 11/08/2010 04:03 PM, djbroadhurst wrote:
      > > Videlicet: How many 7's are there in the largest known prime,
      > > when the latter is written in base 137?
      > >
      > > David (who has no idea, but might be told, eventually)
      >
      > It would be nice to get an answer to this, and edifying to people
      > interested in the problem to see what the bottlenecks are. The number
      > itself, 2^42643801-1, can be calculated with Java (with my patches)
      Expletive!
      I've been running a pfgw script to answer David's question using the above 2^42643801-1 for the past 24 hours.
      I just noticed I should instead be using 2^43112609-1.
      As it appears Kevin will soon have the answer I will not start a second attempt, at least for the time being.
      cheers
      Ken
      > milliseconds (without my patches, several days. It's only a left-shift
      > and a subtract, both of which can be done in small O(n) time.)
      >
      > Converting the radix in native Java will take days and days. Even
      > though it has fast operations for bitCount, that's not much help here.
      > (Even I can do in my head that there will be 42643801 ones and no
      > zeroes, if we only want the binary digits). Scanning the final number
      > for sevens can be done in milliseconds.
      >
      > (My wild estimate, which I may have bungled, is 43853 sevens in the
      > number.)
      >
      > --
      > Alan Eliasen
      > eliasen@...
      > http://futureboy.us/
      >
    • Kevin Acres
      ... You will find, just as in Peter s original script, that the count of zeros has been left as an exercise for the reader. Kevin.
      Message 47 of 47 , Nov 18, 2010
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        At 07:58 PM 18/11/2010, Christ van Willegen wrote:
        >On Thu, Nov 18, 2010 at 9:47 AM, Di Maria Giovanni
        ><calimero22@...> wrote:
        > >
        > > Thank you very much.What'is the sintax of this function c(n,b,v)
        > ?RegardsGiovanni
        >It looks like you should be able to call it like:
        >
        >c(2^43112609-1, 137)
        >
        >IIRC it will return a vector with digit counts for all the digits 0..b-1
        >
        >Christ van Willegen

        You will find, just as in Peter's original script, that the count of
        zeros has been left as an exercise for the reader.

        Kevin.
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