login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A133986 Consecutive prime pairs which after concatenation are prime (ascending or descending order). 2
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 16 21:29 EDT 2021. Contains 345080 sequences. (Running on oeis4.)