[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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