A180679 - OEIS

A180679

Numbers with three distinct prime factors which when concatenated in any order form prime numbers.

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

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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

Table of n, a(n) for n=1..28.

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

Cf. A181559, A217263, A217264, A217265.

Sequence in context: A106724 A239671 A181559 * A251900 A078348 A078963

Adjacent sequences: A180676 A180677 A180678 * A180680 A180681 A180682

KEYWORD

nonn,base

AUTHOR

James Farrington, Sep 15 2010

EXTENSIONS

Missing values inserted by R. J. Mathar, Oct 03 2010

STATUS

approved

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