[seqfan] Re: Primes formed by concatenating other primes.
Paolo Lava
paoloplava at gmail.com
Wed Mar 3 10:05:24 CET 2010
Dear All,
Yes, the two sequences need corrections otherwise they are a mess!
I try to recall in my mind which was the intention…….
As far as I remember the only restriction was not to use twice the same
term.
A141033: delete from 102 to 109.
A141409: delete 293; add 223, 233, 337, 353, 373.
Please check!
Bye
Paolo Lava
2010/3/2 Maximilian Hasler <maximilian.hasler at gmail.com>
> I agree with Franklin's observation.
> Just to avoid confusion, the number "307" I added in the list should
> be ignored (it is not wrong here), it originates from a glitch in my
> PARI code for A019549 which allowed for "leading zeros"
> (307 = 3 + 07).
> (I already submitted the correction and the b-file requested by Eric.)
> I hope this did not cause frustration to anyone...
>
> M.H.
>
> PS: to patch the PARI code, add "& n\10^(i-1)%10 &" before "return"
>
>
> On Tue, Mar 2, 2010 at 7:42 PM, <franktaw at netscape.net> wrote:
> > There are similar problems with A141033 - "Numbers that cannot be
> > formed by the concatenation of previous terms". The example shown of
> > 465 shows that concatenations of 3 or more terms are to be considered.
> > Apparently the intent is to disallow use of the same term twice in the
> > concatenation. But even so, 102 (for example) should not be there.
> >
> > And no, the terms in the concatenation in A141409 need not remain in
> > order; otherwise 73 would be in the sequence. I'm not sure exactly
> > what the intent was, but clearly the sequence contains errors.
> >
> > Franklin T. Adams-Watters
> >
> > -----Original Message-----
> > From: Maximilian Hasler <maximilian.hasler at gmail.com>
> >
> > The sequence
> > A141409
> > Prime numbers that cannot be formed by the concatenation of
> > previous terms.
> >
> > 2, 3, 5, 7, 11, 13, 17, 19, 29, 31, 41, 43, 47, 59, 61, 67, 71, 79,
> > 83, 89, 97, 101, 103, 107, 109, 127, 131, 139, 149, 151, 157, 163,
> > 167, 179, 181, 191, 199, 227, 239, 251, 257, 263, 269, 277, 281, 293,
> > 307, 349, 401, 409, 419, 421, 431, 439, 443, 449, 457, 461
> >
> > has bad terms, e.g. [227, 257, 277, 293, 307, ...]
> >
> > are in A019549 and thus should not be here.
> > (for 227 the question might be if the definition should read "...of
> > TWO previous terms",
> > but this does not explain 293 which is clearly wrong (AFAICS)
> > - or must the terms remain "in order", additionally ?)
> >
> > M.
> >
> >
> >
> > On Tue, Mar 2, 2010 at 6:49 PM, Eric Angelini <Eric.Angelini at kntv.be>
> > wrote:
> >>
> >> Hello SeqFans,
> >> could someone send me please a zipped file with
> >> 10000 terms? I'm looking for something funny!
> >> http://www.research.att.com/~njas/sequences/A019549<http://www.research.att.com/%7Enjas/sequences/A019549>
> >> Best,
> >> É.
> >>
> >>
> >>
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> >>
> >
> >
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