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A117159
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Prime numbers for which the multiplicative digital root is also a prime number.
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1
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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
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OFFSET
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1,1
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LINKS
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EXAMPLE
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157 is in the sequence because it is a prime number and its multiplicative digital root 5 is also a prime number.
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MATHEMATICA
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a[n_]:=NestWhile[Times@@IntegerDigits[#]&, n, #>9&]; Select[Prime[Range[258]], PrimeQ[a[#]]&] (* Jayanta Basu, Jun 02 2013 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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Luc Stevens (lms022(AT)yahoo.com), Apr 21 2006; corrected Apr 30 2006
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STATUS
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approved
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