Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Formula for prime number

  1. Jan 1, 2016 #1
    dear sir, i wish to know if i am correct. a^2+c can be a prime number provided if a is even then c is odd or vice versa, also a and c are not multiple of same number. and c is not a negative square of any number. finally prime number is unique combination of 1,2,and other powers of 2. each power of two is used only once. i wish to know if prime number is bound by it
    thank you
     
  2. jcsd
  3. Jan 2, 2016 #2

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I don't think you have shown more than those are odd numbers. Showing that a number can be prime, because it's odd, is not terribly useful. For a = 3 and b = 2, you getg 11, which is prime. For a = 5 and b = 2 you get 27, which is not.

    I don't understand your last two sentences.
     
  4. Jan 2, 2016 #3

    fresh_42

    Staff: Mentor

    Every integer can be expressed this way. It's the binary or 2-adic representation. (I assume you are talking about integers, although it is not quite clear to me, since you just say "numbers" and "negative squares".)
    If you mean "once and only once" by "only once" it is wrong for ##1+2+4+8 = 15##.
    If you mean "at most once" by "only once" it is wrong since all integers have such a representation.
    So the final answer to your question seems to be: No.
     
  5. Jan 5, 2016 #4
    sir if we add a condition that a^2-c should not be divisible a-c. will this satisfy condition for prime number?
     
  6. Jan 5, 2016 #5

    fresh_42

    Staff: Mentor

    What about ##a = 12## , ##c = 25## ? ##a## is even, ##c## is odd, they don 't have a common divisor, ## a - c = -13 ## does not divide ## a^2 -c = 144 - 25 = 119 = 7 * 17## and ##a^2 + c = 144 + 25 = 13^2## is not prime.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Formula for prime number
  1. Prime number formula (Replies: 6)

  2. Prime Numbers formula (Replies: 69)

  3. Prime Numbers (Replies: 1)

Loading...