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

Author

Enoch Haga, Sep 30 2007

Keywords

• easy
• nonn
• base

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.

Examples

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

Crossrefs

Cf. A088784.

Formula

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

Extensions

Edited by Charles R Greathouse IV, Apr 26 2010