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A069687
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Primes that yield another prime on placing a 1 on both sides (as leading and trailing digits).
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4
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3, 5, 17, 23, 29, 47, 53, 83, 107, 113, 131, 149, 173, 197, 239, 251, 317, 359, 383, 401, 443, 503, 599, 641, 683, 701, 719, 743, 797, 821, 947, 953, 1031, 1049, 1103, 1109, 1187, 1229, 1277, 1283, 1301, 1373, 1583, 1613, 1619, 1637, 1733, 1847, 1889, 1913
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 239 belongs to this sequence as 12391 is also a prime.
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MATHEMATICA
| Select[ Range[2000], PrimeQ[ # ] && PrimeQ[ FromDigits[ Insert[ IntegerDigits[ # ], 1, {{1}, {-1}}]]] &]
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CROSSREFS
| Cf. A069688, A069689 & A069690.
Sequence in context: A027699 A153417 A185022 * A079017 A100564 A154608
Adjacent sequences: A069684 A069685 A069686 * A069688 A069689 A069690
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KEYWORD
| nonn,base
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 06 2002
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EXTENSIONS
| Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), May 03 2002
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