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A117159 Prime numbers for which the multiplicative digital root is also a prime number. 1
2, 3, 5, 7, 13, 17, 31, 37, 43, 53, 71, 73, 113, 131, 137, 151, 157, 173, 211, 223, 311, 317, 359, 367, 389, 431, 557, 571, 593, 673, 751, 827, 839, 929, 953, 983, 1117, 1151, 1153, 1171, 1223, 1279, 1297, 1367, 1447, 1511, 1531, 1553, 1571, 1579, 1597, 1621 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
157 is in the sequence because it is a prime number and its multiplicative digital root 5 is also a prime number.
MATHEMATICA
a[n_]:=NestWhile[Times@@IntegerDigits[#]&, n, #>9&]; Select[Prime[Range[258]], PrimeQ[a[#]]&] (* Jayanta Basu, Jun 02 2013 *)
CROSSREFS
Intersection of A000040 and A028843.
Cf. A031347.
Sequence in context: A048975 A009571 A087520 * A134873 A172979 A118724
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 21 2006; corrected Apr 30 2006
STATUS
approved

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Last modified March 18 21:02 EDT 2024. Contains 370951 sequences. (Running on oeis4.)