[seqfan] Re: A090709 Decimal primes whose decimal representation in base 6 is also prime. -- rebasing -- errata

[Marc LeBrun]

>="Marc LeBrun" <mlb at well.com>
> Thus A090709 might be described succinctly as "primes that when rebased from
> 10 to 6 are prime".

I apologize, this isn't completely accurate.  This definition would also
include 17, which is 13 when rebased from 10 to 6, but could not be mistaken
for a value written in base 6 .

The qualification for "n which look like they could be in base b" is that
10[n]b = n (in my draft notation) or equivalently n_10->b (in Franklin's).

Even so, I favor grounding things on rebasing or similar broad foundation.

For example with rebasing lots of digit string shuffling can be re-expressed
with other numerical or (semi)conventional operations.  For example Knuth's
coefficient operator can be use to pick off individual digits: [x^k] n_10->x
gives the k-th digit of n.