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A046462
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Numbers k such that the concatenation of numbers from 1 to k is the product of 3 primes (not necessarily distinct).
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2
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2, 5, 10, 13, 14, 15, 31, 51, 61, 67, 73
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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FORMULA
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MAPLE
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q:= n-> is(numtheory[bigomega](parse(cat($1..n)))=3):
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MATHEMATICA
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Select[Range[100],
PrimeOmega@FromDigits@Flatten@IntegerDigits@Range@# == 3 &] (* Robert Price, Oct 11 2019 *)
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CROSSREFS
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KEYWORD
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nonn,hard,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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