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A077360
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Primes whose external digits as well as internal digits form a prime.
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4
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127, 131, 137, 139, 151, 157, 173, 179, 223, 229, 233, 239, 331, 337, 421, 431, 433, 457, 523, 631, 677, 733, 739, 751, 773, 823, 829, 839, 853, 859, 937, 977, 1021, 1031, 1033, 1039, 1051, 1117, 1171, 1193, 1231, 1237, 1291, 1297, 1319, 1373, 1433, 1439
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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139 is a member as 19 and 3 are both primes.
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PROG
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(PARI) forprime(p=1, 1440, if(isprime(indigs(p))&&isprime(exdigs(p)), print1(p, ", ")))
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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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EXTENSIONS
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STATUS
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approved
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