[seqfan] Re: Searching for "Sophie Germain 5-almost primes"

Paolo Lava paoloplava at gmail.com
Wed Jan 30 09:28:00 CET 2013


Minimum Sophie Germain n-almost prime number, of course...

2013/1/30 Don Reble <djr at nk.ca>

> ... an integer N with exactly 5 prime factors (not necessarily
>>
>> distinct) such that 2N+1 also has exactly 5 prime factors:
>>
>> 688 = 2^4 * 43
>> 2*688 + 1 = 1377 = 3^4 * 17
>>
>
>    Easy puzzle: what's this?
>
>    2 4 52 40 688 4900 63112 178240 38272 5357056 1997824 247221760
>    586504192 707436544
>
> --
> Don Reble  djr at nk.ca
>
>
>
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