A065723 Primes that when written in base 5, then reinterpreted in base 10, again give primes.

2, 3, 13, 23, 41, 71, 83, 101, 163, 191, 211, 281, 283, 311, 331, 463, 503, 571, 613, 653, 701, 743, 823, 863, 881, 983, 1091, 1213, 1231, 1283, 1301, 1373, 1381, 1423, 1471, 1493, 1531, 1543, 1621, 1741, 1783, 1861, 1873, 1931, 2063, 2203, 2213, 2221

Offset

1,1

Comments

In general rebase notation (Marc LeBrun): p5 = (5) [p] (10).

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Example

E.g., 2213_10 = 32323_5 is prime, and so is 32323_10.

Mathematica

Select[ Range[2250], PrimeQ[ # ] && PrimeQ[ FromDigits[ IntegerDigits[ #, 5]]] & ]
Select[Prime[Range[400]], PrimeQ[FromDigits[IntegerDigits[#, 5]]]&] (* Harvey P. Dale, Mar 28 2015 *)

Prog

(PARI) isok(p)={ isprime(p) && isprime(fromdigits(digits(p, 5))) } \\ Harry J. Smith, Oct 27 2009

Crossrefs

Cf. A065720 up to A065727, A065361.

Sequence in context: A133201 A215302 A103150 * A215134 A177746 A024779

Adjacent sequences: A065720 A065721 A065722 * A065724 A065725 A065726

Keyword

nonn,base

Author

Patrick De Geest, Nov 15 2001

Status

approved