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A086042
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Nontrivial numbers which are prime and yield another prime when their digits are sorted in ascending order.
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3
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31, 71, 73, 97, 101, 103, 107, 109, 131, 173, 193, 197, 271, 293, 307, 311, 317, 373, 397, 419, 439, 491, 509, 547, 571, 593, 607, 617, 647, 659, 673, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 809, 839, 907, 919, 937, 941, 947, 953, 971, 983, 991
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OFFSET
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1,1
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COMMENTS
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Primes with digits already in ascending order (like 13 and 2357) are trivial cases and are therefore excluded.
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LINKS
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EXAMPLE
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a(1)=31 because an ascending sort of 31's digits yields 13 which is also prime. a(53)=1009 because an ascending sort of 1009's digits yields 19 which is also prime.
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MATHEMATICA
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paoQ[n_]:=Module[{idn=IntegerDigits[n], sidn}, sidn=Sort[idn]; sidn!=idn && PrimeQ[FromDigits[sidn]]] (* Harvey P. Dale, Nov 14 2011 *)
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PROG
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(PARI) select( is_A086042(p, q=fromdigits(vecsort(digits(p))))={p>q&&isprime(q)&&isprime(p)}, [1..999]) \\ M. F. Hasler, Jul 30 2019
(Magma) [p:p in PrimesUpTo(1000)| IsPrime(Seqint(Reverse(Sort(Intseq(p, 10))))) and p ne Seqint(Reverse(Sort(Intseq(p, 10)))) ]; // Marius A. Burtea, Jul 30 2019
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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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Chuck Seggelin (barkeep(AT)plastereddragon.com), Jul 07 2003
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STATUS
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approved
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