[seqfan] Do emirpimes with leading zeroes count?

Alonso Del Arte alonso.delarte at gmail.com
Wed Dec 22 18:58:43 CET 2010

In editing A119684, R. J. Mathar raised a very interesting point which is
moot in base 10 but very relevant in prime bases, like ternary:

Are multiples of the base, those numbers that end with zeroes, eligible for
consideration as emirpimes, since their trailing zeroes will become leading
zeroes upon reversal? For example, in ternary, 1220 becomes 0221, which is
the square of 12, a prime.

The Mathematica program I added to the sequence includes the condition
gcd(n, 3) = 1; a simple cut allows the computer to consider numbers that are
multiples of the base (a necessary provision only in prime bases if the
concept of emirpimes is meant to exclude multiples of the base).


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