# [seqfan] Re: Triples of 3-digit primes using together digits 1..9.

Ray Chandler rayjchandler at sbcglobal.net
Wed Jul 7 22:45:21 CEST 2010

```I believe Zak counted the ordered triples (p1<p2<p3) whereas Harvey's code
counts triples without regard for order.

I would expect Harvey's number to 6 times Zak's number, and it is.
Ray

> -----Original Message-----
> From: seqfan-bounces at list.seqfan.eu
> [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Harvey P. Dale
> Sent: Wednesday, July 07, 2010 2:28 PM
> To: Sequence Fanatics Discussion list
> Subject: [seqfan] Re: Triples of 3-digit primes using
> together digits 1..9.
>
> Zak:
>
> 	I think there are 816 such triples.  This Mathematica
> program will generate them in the form of 9-digit numbers.
>
> okQ[n_] :=
>  Module[{idn = FromDigits /@ Partition[IntegerDigits[n], 3]},
>   PrimeQ[idn[[1]]] && PrimeQ[idn[[2]]] && PrimeQ[idn[[3]]]]
> Select[FromDigits /@ Permutations[Range[9]], okQ]
>
> 	Best,
>
> 	Harvey
>
> -----Original Message-----
> From: seqfan-bounces at list.seqfan.eu
> [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of zak seidov
> Sent: Tuesday, July 06, 2010 10:24 AM
> To: seqfaneu
> Subject: [seqfan] Triples of 3-digit primes using together
> digits 1..9.
>
> Triples of 3-digit primes,
> using together digits 1..9.
> There are 136 such triples,
> from {127,463,859} to {659,743,821}.
>
> http://zak08.livejournal.com/23029.html
>

```