# [seqfan] Re: Two make a prime

Maximilian Hasler maximilian.hasler at gmail.com
Sat Nov 9 12:22:11 CET 2013

```PS: One could also consider positive integers only, then the sequence is
1,3,2,9,5,11,8,12,4,7,6,10,13,15,14,17,18,16,19,21,22,30,20,23,24,29,26,27,25,31,28,33,32,35,36,34,37,39,38,41,42,43,45,47,44,51,40,49,46,57,50,53,48,59,56,63,52,61,54,67,55,69,58,70,60,71,62,72,64,73,66,79,75,65,74,68,77,78,76,81,80,83,86,87,82,90,85,91,84,89,92,...
(The first one is proposed as https://oeis.org/draft/A231433)
Maximilian

On Sat, Nov 9, 2013 at 6:54 AM, Maximilian Hasler
<maximilian.hasler at gmail.com> wrote:
> Dear Eric,
> thanks for the nice start into the week-end! This one is very easy to program:
> a=u=0;for(n=1,99,u+=1<<a;print1(a",");for(k=1,9e9,bittest(u,k)&&next;d=Vec(Str(a,k));for(p=0,(#d)!-1,isprime(eval(concat(t=vecextract(d,numtoperm(#d,p)))))&&t[1]>"0"&&(a=k)&&next(3))))
> 0,11,2,3,1,4,7,6,10,9,5,12,8,18,13,15,14,17,20,23,21,16,19,22,30,25,27,26,29,24,31,28,33,32,35,36,
> 34,37,39,38,41,42,43,45,47,44,51,40,49,46,57,50,53,48,59,56,63,52,61,54,67,55,69,58,70,60,71,62,
> 72,64,73,66,79,75,65,74,68,77,78,76,81,80,83,86,87,82,90,85,91,84,89,92,93,88,94,96,95,98,99,...
>
> Best wishes,
> Maximilian
>
> On Sat, Nov 9, 2013 at 6:28 AM, Eric Angelini <Eric.Angelini at kntv.be> wrote:
>>
>> Hello SeqFans,
>> following my former post, the same idea
>> could be applied to primes:
>>
>> Pr = 0,11,2,3,1,7,4,10,9,8,12,5,...
>>
>> Again, I guess, a permutation of 1,2,3,4,5,...+oo.
>>
>> 0 and 11 produce 101, a prime
>> 11 and 2 produce 211, a prime
>> 2 and 3 produce 23
>> 3 and 1 produce 13
>> 1 and 7 produce 17
>> 7 and 4 produce 47
>> 4 and 10 produce 401
>> 10 and 9 produce 109
>> 9 and 8 produce 89
>> 8 and 12 produce ...
>> etc.
>>
>> Best,
>> É.
>>
>> Propulsé d'un aPhone
>>
>>
>>
>> _______________________________________________
>>
>> Seqfan Mailing list - http://list.seqfan.eu/
```