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A046503
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Primes with multiplicative persistence value 3.
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3
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47, 59, 79, 89, 97, 139, 149, 157, 179, 193, 197, 227, 229, 239, 263, 283, 293, 337, 347, 353, 359, 367, 373, 383, 389, 419, 433, 443, 449, 463, 479, 487, 491, 499, 571, 577, 593, 619, 643, 661, 673, 683, 691, 719, 733, 743, 751, 757, 797, 823, 829, 839
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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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47 -> 4 * 7 -> [ 28 ] -> 2 * 8 -> [ 16 ] -> 1 * 6 -> [ 6 ] -> one digit in three steps.
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MAPLE
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filter:= proc(n) local L;
if not isprime(n) then return false fi;
L:= convert(convert(n, base, 10), `*`); if L < 10 then return false fi;
L:= convert(convert(L, base, 10), `*`); if L < 10 then return false fi;
L:= convert(convert(L, base, 10), `*`); evalb(L < 10)
end proc:
select(filter, [seq(i, i=11..1000, 2)]); # Robert Israel, Jun 05 2018
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MATHEMATICA
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pr3Q[n_] := Length[NestWhileList[Times @@ IntegerDigits[#] &, n, # > 9 &]] == 4; Select[Prime[Range[147]], pr3Q] (* Jayanta Basu, Jun 26 2013 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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