Timeline for Prime numbers $p$ not of the form $ab + bc + ac$ $(0 < a < b < c )$ (and related questions)
Current License: CC BY-SA 2.5
4 events
| when toggle format | what | by | license | comment | |
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| Nov 21, 2009 at 21:08 | comment | added | Kristal Cantwell | If a Sophie Germain prime p is of the form 2q+1 where q is prime then p+1/2-1 is prime so it looks like it will make a difference. Look at 37 37+1 = 38 =2*19 and your agument breaks down but 37 is not a Sophie Germain prime or a matching safe prime because it is equal to 1 mod 6 not 5 mod six. I think your argument works for everything except p and 2p-1 paris which is different from p, 2p+1 of the Sophie Germain prime | |
| Nov 21, 2009 at 20:36 | comment | added | Kristal Cantwell | I looked at the wikipedia entry for Sophie Germain prime and it stated it as a prime p where 2p+1 is prime. Your argument still works though p must not be 2q+1 where q is a Sophie Germain prime or it must not be the matching safe prime of a Sophie Germain prime. | |
| Nov 21, 2009 at 20:24 | history | edited | David E Speyer | CC BY-SA 2.5 |
added 33 characters in body
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| Nov 21, 2009 at 20:10 | history | answered | David E Speyer | CC BY-SA 2.5 |