Obviousness of Primeness
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Excuse the title, I'm spicing up a Sunday evening fixing bugs. What is that makes so many small numbers obviously prime when I look at them? Is this a result of having learned all my 'times tables', or is there some characteristic of the digits that conveys this? E.g. 41 just looks prime, as does 83, or 97. These are just 'obvious primes' off the top of my head. Going further, 153 is obvious, as is 2011.
Pits fall into Chuck Norris.
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Excuse the title, I'm spicing up a Sunday evening fixing bugs. What is that makes so many small numbers obviously prime when I look at them? Is this a result of having learned all my 'times tables', or is there some characteristic of the digits that conveys this? E.g. 41 just looks prime, as does 83, or 97. These are just 'obvious primes' off the top of my head. Going further, 153 is obvious, as is 2011.
Pits fall into Chuck Norris.
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51 is another obvious prime non-prime.
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51 is another obvious prime non-prime.
I was about to note that. I guess the 'looks prime' factor is then influenced by in-grained knowledge of 'times tables' for lower numbers, because as they get higher, there are just too many options. My first guess was based on "the 3 must come from 13 or 43" etc. and I missed 63. If we stick to numbers under say 100, this guessing is a lot more accurate.
Pits fall into Chuck Norris.
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I was about to note that. I guess the 'looks prime' factor is then influenced by in-grained knowledge of 'times tables' for lower numbers, because as they get higher, there are just too many options. My first guess was based on "the 3 must come from 13 or 43" etc. and I missed 63. If we stick to numbers under say 100, this guessing is a lot more accurate.
Pits fall into Chuck Norris.
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The distribution of prime numbers correlates closely to log something.
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-SK Genius
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Excuse the title, I'm spicing up a Sunday evening fixing bugs. What is that makes so many small numbers obviously prime when I look at them? Is this a result of having learned all my 'times tables', or is there some characteristic of the digits that conveys this? E.g. 41 just looks prime, as does 83, or 97. These are just 'obvious primes' off the top of my head. Going further, 153 is obvious, as is 2011.
Pits fall into Chuck Norris.
I've heard it claimed that 91 is the smallest non-prime that looks prime. This is because it fails all the usual tests (divisibility by 2,3,5) and is not in any of the times tables that we learn.
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