A133986 Consecutive prime pairs which after concatenation are prime (ascending or descending order).

23, 53, 3137, 5347, 5953, 6761, 8389, 137131, 151157, 157163, 167173, 179173, 199211, 211199, 223211, 233239, 239233, 257263, 263257, 263269, 271277, 331337, 353359, 359353, 373379, 433439, 467479, 509521, 523541, 541523, 541547, 593587

Offset

1,1

Comments

For the range above the prime concatenations occur after a mean of 3.1579 trials. Some primes are interlocking, as many as three in succession.

Links

Table of n, a(n) for n=1..32.

Formula

Select consecutive prime pairs, concatenate and test for primality (ascending and descending order)

Example

5347 is a member: 53 and 47, prime; 4753 was also tested, but is composite.

Crossrefs

Cf. A088784.

Sequence in context: A078959 A238854 A045345 * A103006 A053236 A118603

Adjacent sequences: A133983 A133984 A133985 * A133987 A133988 A133989

Keyword

easy,nonn,base

Author

Enoch Haga, Sep 30 2007

Extensions

Edited by Charles R Greathouse IV, Apr 26 2010

Status

approved