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Search: id:A069689
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| A069689 |
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Primes that yield another prime on placing a 7 on both sides (as leading and trailing digits). |
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+0
4
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| 2, 5, 17, 23, 29, 41, 47, 53, 71, 131, 191, 227, 233, 257, 281, 293, 347, 359, 389, 401, 419, 431, 479, 503, 521, 557, 593, 599, 653, 659, 677, 683, 701, 761, 797, 827, 857, 887, 953, 977, 1091, 1097, 1109, 1151, 1181, 1187, 1193, 1223, 1283, 1307, 1373
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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233 is a member as 72337 is also a prime.
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MATHEMATICA
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Select[ Range[2000], PrimeQ[ # ] && PrimeQ[ FromDigits[ Insert[ IntegerDigits[ # ], 7, {{1}, {-1}}]]] &]
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CROSSREFS
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Cf. A069687, A069688 & A069690.
Sequence in context: A075612 A041283 A042049 this_sequence A106021 A032605 A099243
Adjacent sequences: A069686 A069687 A069688 this_sequence A069690 A069691 A069692
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KEYWORD
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nonn,base
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 06 2002
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), May 03 2002
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