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A057630
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Primes such that replacing each digit d with d copies of the digit d produces a prime. Zeros are allowed.
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2
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11, 31, 53, 101, 131, 149, 223, 283, 311, 313, 331, 397, 463, 503, 641, 691, 937, 941, 1031, 1049, 1069, 1301, 1409, 1439, 1511, 1609, 1741, 1871, 1949, 1993, 1999, 2083, 2111, 2203, 2447, 2803, 2939, 3001, 3011, 3061, 3163, 3301, 3391, 3433, 3499, 3559
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history;
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OFFSET
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1,1
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COMMENTS
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"Replacing each digit d with d copies of the digit d" is the function A048376, well defined on the set of positive integers. Therefore (the range of) the present sequence is the largest subset of A000040 stable under the operation A048376.
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LINKS
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Table of n, a(n) for n=1..46.
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EXAMPLE
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E.g. 641 becomes 66666644441 which is also prime.
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MATHEMATICA
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Select[Prime[Range[500]], PrimeQ[FromDigits[Flatten[Table[#, {#}]&/@IntegerDigits[#]]]]&] [From Harvey P. Dale, Dec. 18, 2010]
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PROG
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(PARI) is_A057630(n)={isprime(A048376(n)) && isprime(n)} \\ - M. F. Hasler, Jan 23 2013
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CROSSREFS
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Cf. A057628.
Sequence in context: A043904 A152293 A031287 * A057628 A144364 A031372
Adjacent sequences: A057627 A057628 A057629 * A057631 A057632 A057633
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KEYWORD
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nonn,base,nice,easy
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AUTHOR
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G. L. Honaker, Jr., Oct 10 2000
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EXTENSIONS
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More terms from Patrick De Geest, Oct 15 2000.
Offset changed to 1, according to OEIS conventions, by M. F. Hasler, Jan 23 2013
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STATUS
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approved
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