[seqfan] Another "interpret this sequence!" brainteaser

Charles Greathouse charles.greathouse at case.edu
Mon Aug 2 23:53:56 CEST 2010

A140532 is "a(n) = number of n-digit pandigital primes."  In the
examples, it considers all primes below 100 *except* 11 to be

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
Case Western Reserve University

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