

A235637


Primes whose base7 representation also is the base6 representation of a prime.


1



2, 3, 5, 19, 61, 89, 127, 131, 173, 211, 229, 257, 281, 383, 397, 421, 463, 467, 523, 547, 593, 617, 719, 757, 761, 859, 883, 911, 953, 967, 971, 1069, 1097, 1153, 1163, 1181, 1303, 1307, 1429, 1433, 1471, 1489, 1531, 1583, 1597, 1723, 1741, 1867, 1877, 1951, 1979, 1993, 2437
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OFFSET

1,1


COMMENTS

This sequence is part of the twodimensional 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.


LINKS

Table of n, a(n) for n=1..53.
M. F. Hasler, Primes whose base c expansion is also the base b expansion of a prime


EXAMPLE

E.g., 19 = 25_7 and 25_6 = 17 are both prime.


PROG

(PARI) is(p, b=6, c=7)=vecmax(d=digits(p, c))<b&&isprime(vector(#d, i, b^(#di))*d~)&&isprime(p)
(PARI) forprime(p=1, 3e3, is(p, 7, 6)&&print1(vector(#d=digits(p, 6), i, 7^(#di))*d~, ", ")) \\ To produce the terms, this is more efficient than to select them using straightforwardly is(.)=is(., 6, 7)


CROSSREFS

Cf. A235636, 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: A031133 A352604 A235622 * A028490 A004064 A164061
Adjacent sequences: A235634 A235635 A235636 * A235638 A235639 A235640


KEYWORD

nonn,base


AUTHOR

M. F. Hasler, Jan 13 2014


STATUS

approved



