discrete math- sequence question

Discussion in 'Homework Help' started by s3b4k, Mar 8, 2010.

  1. s3b4k

    s3b4k Thread Starter Member

    Joined:
    Feb 15, 2010
    Messages:
    38
    I need to come up with a rule or a formula for the following:

    1,2,2,2,3,3,3,3,3,5,5,5,5,5,5,5.....
  2. someonesdad

    someonesdad Senior Member

    Joined:
    Jul 7, 2009
    Messages:
    1,584
    Location:
    Northwest USA
    Hint: 2*n + 1 and primes
  3. jpanhalt

    jpanhalt E-book Developer

    Joined:
    Jan 18, 2008
    Messages:
    4,043
    Location:
    Ohio, USA(GMT-5)
    There may be more than one pattern that gives that initial sequence. One solution is: the digits 1,2,3,and 5 are primes (positive). The repeat frequencies seem to follow just the odd numbers. The next three repeat frequencies would be 9, 11 and 13. That is, the next two sequences would be nine 7's, then eleven 11's.

    John
    s3b4k likes this.
  4. s3b4k

    s3b4k Thread Starter Member

    Joined:
    Feb 15, 2010
    Messages:
    38
    ok thanks a lot for the help, but is there an exact formula i can use, or is it only solvable by explaining it?
  5. Markd77

    Markd77 Senior Member

    Joined:
    Sep 7, 2009
    Messages:
    2,801
    Location:
    Birmingham
    1 isn't normally considered a prime if that makes any difference.
  6. jpanhalt

    jpanhalt E-book Developer

    Joined:
    Jan 18, 2008
    Messages:
    4,043
    Location:
    Ohio, USA(GMT-5)
  7. Markd77

    Markd77 Senior Member

    Joined:
    Sep 7, 2009
    Messages:
    2,801
    Location:
    Birmingham
    I searched for the sequence on google and found this. Still no idea what it is.
  8. jpanhalt

    jpanhalt E-book Developer

    Joined:
    Jan 18, 2008
    Messages:
    4,043
    Location:
    Ohio, USA(GMT-5)
    For (b) the sequence starts with 1, and if there are at least 2 previous term, then the subsequent term is the sum of the previous two terms, otherwise it is 2 (or alternatively, the previous term is doubled). The replicates of each term is as in the first problem.

    I am too tired to look at (a) now. Perhaps this question should have its own thread.

    John

    Edit: For (a) here's a reference: http://mathworld.wolfram.com/Near-SquarePrime.html
    Last edited: Mar 11, 2010
  9. s3b4k

    s3b4k Thread Starter Member

    Joined:
    Feb 15, 2010
    Messages:
    38
    this question is driving me nuts, are the next three terms going to be 8,8,8 or 7,7,7. because it good either be prime numbers or just the sum of the previous numbers, but if its the sum of the previous numbers how do you get the two there
  10. jpanhalt

    jpanhalt E-book Developer

    Joined:
    Jan 18, 2008
    Messages:
    4,043
    Location:
    Ohio, USA(GMT-5)
    There is not enough information to know for sure. The sum of the previous numbers (Fibonacci, 8) may be what your teacher wants. In either case, you have to make an explanation for the first number (or absence thereof).

    John

    PS, when I went to school 1 was still prime. But then, it was a public school.
    s3b4k likes this.

Share This Page