[seqfan] Re: Another "interpret this sequence!" brainteaser
Alois Heinz
heinz at hs-heilbronn.de
Tue Aug 3 00:40:53 CEST 2010
The sequence seems to count n-digit primes (in decimal notation) which have
no digit 0 and no repeated digits.
keywords: base, fini, ...
"pandigital" in description is misleading
Charles Greathouse schrieb:
> A140532 is "a(n) = number of n-digit pandigital primes." In the
> examples, it considers all primes below 100 *except* 11 to be
> pandigital.
>
> The first interpretation that came to mind was that the sequence was
> counting primes without repeated digits. But this gives |{103, ...,
> 983}| = 97 for a(3), while the sequence has 83. (There are 143
> 3-digit primes, so it's leaving out 60.)
>
> Any ideas? The sequence cites
> Clifford A. Pickover, Wonders of Numbers.
> Schaum's Outlines, Combinatorics, see inclusion/exclusion principle
> as references, but I don't think the sequence appears in either, based
> on a Google Book search.
>
> Charles Greathouse
> Analyst/Programmer
> Case Western Reserve University
>
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