# [seqfan] Re: Two make a prime

Maximilian Hasler maximilian.hasler at gmail.com
Sat Nov 9 11:54:24 CET 2013

```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
>
>
>
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>
> Seqfan Mailing list - http://list.seqfan.eu/
```