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Search: id:A091898
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| A091898 |
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Numbers that change from composite to prime or vice versa for at least one permutation of their digits. |
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+0
2
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| 14, 16, 19, 20, 23, 29, 30, 32, 34, 35, 38, 41, 43, 47, 50, 53, 59, 61, 67, 70, 74, 76, 83, 89, 91, 92, 95, 98, 101, 103, 104, 106, 107, 109, 110, 112, 115, 118, 119, 121, 124, 125, 127, 128, 130, 133, 134, 136, 137, 139, 140, 142, 143, 145, 146, 149, 151, 152, 154
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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This is actually a subsequence of the complement of A091897, the union of A003459 and A067012: This sequence contains no powers of 10 (A011557) as 1 is not prime.
Clearly also no repdigit number (A010785) is a term nor is any number with only even digits (except for 20,200,2000,...) nor is any number divisible by 3 (except for 30,300,3000,...). Among other primes, this sequence does include all primes p > 5 which contain at least one of the digits 0,2,4,5,6,8.
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EXAMPLE
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14=2*7 (composite) is a term as a permutation of its digits gives 41 (prime).
Hence 41 is also a term. 19 (prime) is a term as 91=7*13 (composite). Thus 91
is also a term. 130=2*5*13 (composite) is a term (even though the permutation
310=2*5*31 is also composite) because another permutation (0)13 (prime) exists
(dropping the leading 0). 13, however, is not a term as 31 is also prime (13
and 31 are members of A003459).
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CROSSREFS
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Cf. A003459 (absolute primes), A067012 ('absolute composites'), A091897 (union of A003459 and A067012), A010785 (repdigit numbers).
Sequence in context: A158282 A053425 A034305 this_sequence A061365 A102107 A007935
Adjacent sequences: A091895 A091896 A091897 this_sequence A091899 A091900 A091901
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KEYWORD
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base,nonn
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AUTHOR
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Rick L. Shepherd (rshepherd2(AT)hotmail.com), Feb 09 2004
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