Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
Robert Price, <a href="/A235470/b235470_1.txt">Table of n, a(n) for n = 1..829</a>
reviewed
approved
proposed
reviewed
editing
proposed
Robert Price, <a href="/A235470/b235470_1.txt">Table of n, a(n) for n = 1..829</a>
approved
editing
reviewed
approved
proposed
reviewed
editing
proposed
Primes whose base -7 representation also is the base -3 representation of a prime.
This sequence is part of the two -dimensional array of sequences based on this same idea for any two different bases b, c > 1. Sequence A235265 and A235266 are the most elementary ones in this list. Sequences A089971, A089981 and A090707 through A090721, and sequences A065720 - A065727, follow the same idea with one base equal to 10.
Since the trailing digit of the base -7 expansion must (like all others) be less than 3, this is a subsequence of A045381.
E.g., 7 = 10[_7] and 10[_3] = 3 are both are prime; 107 = 212[_7] and 212[_3] = 23 are both are prime.
approved
editing
editing
approved