login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A180679 Numbers with three distinct prime factors which when concatenated in any order form prime numbers. 4
3311, 27181, 32153, 41237, 53977, 86507, 110971, 125069, 208579, 256413, 500981, 543337, 853811, 901949, 964481, 1053787, 1144171, 1197851, 1215731, 1344539, 1385189, 1433659, 1549603, 1674741, 1681547, 1699481, 1973479, 2028181 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The sequence admits only numbers with three distinct prime factors. A denser sequence (a superset) is obtained if prime factors may be repeated. [From R. J. Mathar, Oct 03 2010]
There is no term with four distinct prime factors under 10^8. [From Dmitri Kamenetsky, Sep 29 2012]
LINKS
EXAMPLE
For 3311, 3311=7 * 11 * 43, and 71143, 74311, 43711, 43117, 11437, 11743 are all prime numbers.
MATHEMATICA
Take[Union[Times @@@ Select[Subsets[Prime[Range[300]], {3}], And @@ PrimeQ[FromDigits /@ (Flatten /@ (IntegerDigits /@ Permutations[#]))] &]], 30] (* Harvey P. Dale, Jan 29 2011 *)
CROSSREFS
Sequence in context: A106724 A239671 A181559 * A251900 A078348 A078963
KEYWORD
nonn,base
AUTHOR
James Farrington, Sep 15 2010
EXTENSIONS
Missing values inserted by R. J. Mathar, Oct 03 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)