

A235630


Primes whose base 7 representation is also the base 8 representation of a prime.


1



2, 3, 5, 17, 47, 71, 89, 101, 197, 229, 241, 269, 271, 337, 353, 383, 479, 521, 577, 607, 631, 647, 673, 677, 719, 743, 761, 827, 997, 1097, 1153, 1181, 1193, 1279, 1289, 1303, 1319, 1447, 1543, 1601, 1697, 1811, 1823, 1907, 1951, 1993, 2017, 2131, 2203, 2243, 2339, 2357, 2383, 2549
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OFFSET

1,1


COMMENTS

This sequence is part of a two dimensional array of sequences, given in the LINK, 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.


LINKS

Table of n, a(n) for n=1..54.
M. F. Hasler, Primes whose base c expansion is also the base b expansion of a prime


EXAMPLE

E.g., 17 = 23[7] and 23[8] = 19 both are prime.


PROG

(PARI) is(p, b=8, c=7)=isprime(vector(#d=digits(p, c), i, b^(#di))*d~)&&isprime(p) \\ NB: This code is only valid for b>c.


CROSSREFS

Cf. A235622, A235265, A235266, A152079, A235461  A235482, A065720  A065727, A235394, A235395, A089971 ⊂ A020449, A089981, A090707  A091924, A235615  A235639. See the LINK for further crossreferences.
Sequence in context: A243441 A256426 A019350 * A235636 A268130 A103074
Adjacent sequences: A235627 A235628 A235629 * A235631 A235632 A235633


KEYWORD

nonn,base


AUTHOR

M. F. Hasler, Jan 13 2014


STATUS

approved



