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shahzadjalbani Group Title

Is there any equation to calculate the prime numbers?

  • 2 years ago
  • 2 years ago

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  1. nbouscal Group Title
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    Nope

    • 2 years ago
  2. lgbasallote Group Title
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    do you mean a formula to verify if it is prime?

    • 2 years ago
  3. shahzadjalbani Group Title
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    Yes.....

    • 2 years ago
  4. nbouscal Group Title
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    There are a lot of methods for finding prime numbers, but it's not that easy, there's no function to check if any number is prime without having a list of prime numbers to use

    • 2 years ago
  5. nbouscal Group Title
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    Sieve of Eratosthenes is a good place to start if you want to research this area

    • 2 years ago
  6. lgbasallote Group Title
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    i can come up with a formula impromptu....o.O

    • 2 years ago
  7. lgbasallote Group Title
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    but yeah...there isnt any im familiar of

    • 2 years ago
  8. ParthKohli Group Title
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    Easiest way: check if it's divisible by any natural number or not :P

    • 2 years ago
  9. nbouscal Group Title
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    Trust me the number theorists would love if there was an easy formula to verify primality :P

    • 2 years ago
  10. nbouscal Group Title
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    So far, there isn't. If there was the Reimann Hypothesis wouldn't be as big of a deal as it is.

    • 2 years ago
  11. ParthKohli Group Title
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    I see something interesting. http://en.wikipedia.org/wiki/Lucas%E2%80%93Lehmer_primality_test

    • 2 years ago
  12. lgbasallote Group Title
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    here is a list of *some* prime numbers if itll help: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997

    • 2 years ago
  13. nbouscal Group Title
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    Yeah parth that is for Mersenne primes only, though

    • 2 years ago
  14. ParthKohli Group Title
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    ^ spam. It didnt help

    • 2 years ago
  15. lgbasallote Group Title
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    are you good now @shahzadjalbani ?

    • 2 years ago
  16. shahzadjalbani Group Title
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    @lgbasallote You sent a list of numbers now I have to compare each number with this list it will more difficult and lengthy job . Is there any simple way to do it .

    • 2 years ago
  17. nbouscal Group Title
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    There is not a simple way with the primes. The primes are not simple. That's why people are still studying them :)

    • 2 years ago
  18. lgbasallote Group Title
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    my way is bloodily and manually divide a number by the simplest prime numbers (2, 3, 5, 7, 11) if i get a quotient with no remainder it is not prime....if there is a remainder...i have no way f knowing so i give up and say true lol

    • 2 years ago
  19. lgbasallote Group Title
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    i have no way of knowing because the number could be divisible by the succeeding prime numbers or it could be just prime

    • 2 years ago
  20. nbouscal Group Title
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    One important method when determining if a number is prime is to bound the potential divisors by the square root of the number you're investigating. Once you hit that bound, you know it's prime.

    • 2 years ago
  21. lgbasallote Group Title
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    but normally...if the number is not divisible by the basic prime numbers then it is prime...teachers are not that sadistic to have you try each one

    • 2 years ago
  22. shahzadjalbani Group Title
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    @nbouscal explain your statement.

    • 2 years ago
  23. nbouscal Group Title
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    Well, any integer divisors come in pairs, right? So if you're looking at the number 20, for example, you have pairs 1,20; 2, 10; 4, 5... then you have 5,4; 10,2; 20,1... but you already had those, just backwards. So if you're checking primes, and you check 1, 2, 4... you don't need to check any more numbers past that because you already would have found it in those first pairs. Once you hit the square root of the number, you know you don't have to check anymore.

    • 2 years ago
  24. lgbasallote Group Title
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    or just divide by the primes

    • 2 years ago
  25. nbouscal Group Title
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    So for example you want to check if 51 is prime, and you know that sqrt(51) is just a bit over 7, you only have to check if 51 is divisible by 2, 3, 5, 7. You don't need to go any further than that.

    • 2 years ago
  26. lgbasallote Group Title
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    20/2 wields a quotient with no remainder so it is automatically not prime

    • 2 years ago
  27. nbouscal Group Title
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    Obviously 20 isn't prime, lgba, that was not the point of the example.

    • 2 years ago
  28. lgbasallote Group Title
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    i was giving an eample too...of my method

    • 2 years ago
  29. nbouscal Group Title
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    The point was to show why you don't need to worry about primes greater than the square root, because you would already have run into them before you got to the square root.

    • 2 years ago
  30. lgbasallote Group Title
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    makes sense...

    • 2 years ago
  31. nbouscal Group Title
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    The square root bound is very useful when you are using computer methods to check primality on large numbers, it saves a lot of time.

    • 2 years ago
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