mersenneforum.org Primorial puzzle
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 2006-03-07, 03:17 #1 Citrix     Jun 2003 62B16 Posts Primorial puzzle Find the number of numbers under P# that are not divisible by any of the primes under p. (including p) I am interested in an exact number not an approximate prediction. Describe such an algorithm. Have fun!!!
 2006-03-07, 04:51 #2 grandpascorpion     Jan 2005 Transdniestr 503 Posts Priminusal The odds of the number being p unsmooth is: 1/2*2/3*4/5*6/7 ... (p-1)/p The denominator = p#. You multiply the probability by the sample size to get the count of numbers. The sample is size is p#. So, p#'s cancel and you are left with: The answer is 1* 2 * 4 * 6 ... *(p-1). I dub this the Priminusal
 2006-03-07, 06:08 #3 Citrix     Jun 2003 1,579 Posts Any other methods, I know that is the answer? I have a method in mind that leads to this formula, anyone want to guess? Citrix edit:- Does the ratio approach a value? 1/2*2/3*4/5*6/7 ... (p-1)/p Last fiddled with by Citrix on 2006-03-07 at 06:16
 2006-03-07, 15:07 #4 grandpascorpion     Jan 2005 Transdniestr 1111101112 Posts Why in the world would you need another answer or method? This is basic stuff.

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