[seqfan] Number of primes having distinct first and last digits both 7 to 10^n primes

Charles Greathouse charles.greathouse at case.edu
Mon Aug 2 22:21:28 CEST 2010


A145711 is defined as "Number of primes having distinct first and last
digits both 7 to 10^n primes".  It seems to mean something similar to
"Number of primes below 10^n with distinct first and last decimal
digits", but this isn't quite it.  Can anyone decipher it?

>From its description:
Comment: The first prime with equal first and last digits is 11 -- the
two digits must be distinct, so 7, for example, cannot be
double-counted.
Example: a(3)=32 because to 10^3 or 1000 primes, ending in 7919, there
are 32 primes with equal and distinct first and last digits: 7 and 7.

It also needs keyword work: it needs "base" but not "easy" (since it
involves exponentially many terms).

Charles Greathouse
Analyst/Programmer
Case Western Reserve University




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