[seqfan] Re: Fwd: Right truncatable primes
Martin Fuller
martin_n_fuller at btinternet.com
Fri Oct 31 21:18:00 CET 2008
Would a kind SeqFan confirm the value of A076623(12) for me? OEIS lists the result as 170051 and I calculate 170053.
A076623 Total number of left truncatable primes (without zeros) in base n.
Martin Fuller
--- On Tue, 28/10/08, Olivier Gerard <olivier.gerard at gmail.com> wrote:
> From: Olivier Gerard <olivier.gerard at gmail.com>
> Subject: [seqfan] Fwd: Right truncatable primes
> To: seqfan at seqfan.eu
> Date: Tuesday, 28 October, 2008, 5:31 PM
> Hello seqfans,
>
> This is a recent post in the Number Theory List
> which might be of interest to member.
>
> Please, put Kurt Foster in copies of your answers
> to the list.
>
> Olivier
>
>
>
> ---------- Forwarded message ----------
> From: Kurt Foster <drsardonicus at earthlink.net>
> Date: Tue, Oct 28, 2008 at 18:25
> Subject: Right truncatable primes
> To: NMBRTHRY at listserv.nodak.edu
>
>
> I recently revived an interest in these things (which
> I'll call
> rtp's), and Phil Carmody has made some heroic
> computations to find the
> number of base-b rtp's for a steadily-increasing list
> of b's.
>
> A list of the number of base-b rtps up to base fifty-three
> is listed
> in the OEIS at
>
> http://www.research.att.com/~njas/sequences/A076586<http://www.research.att.com/%7Enjas/sequences/A076586>
>
> There is also a paper,
>
> Angell, I. O. and Godwin, H. J. "On Truncatable
> Primes." Math. Comput.
> 31, 265-267, 1977.
>
> I don't have access to electronic archives, so I was
> wondering if
> someone could get me at least a summary of what's in
> that paper.
>
> I concocted a ridiculously simple model to estimate the
> number of base-
> b rtp's with k digits in terms of b and k. I was very
> surprised at
> how well it estimated the value of k for which the number
> of k-digit
> rtp's is a maximum, and also the largest k for which
> there are any k-
> digit base-b rtp's. It's not bad but also not
> terribly good at
> estimating the total number of base-b rtp's in terms of
> b, but I
> figured that before trying to refine my model, I should
> make sure I
> wasn't just re-inventing the wheel.
>
> If anyone knows the above-mentioned paper, or of any more
> recent work
> on these beasties, please let me know.
>
> Thanks, KF
>
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