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A059677
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Numbers n such that 1n1, 3n3, 7n7 and 9n9 are all primes.
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2
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20, 53, 341, 536, 2312, 2477, 3380, 3665, 3686, 4547, 5009, 5105, 6458, 6488, 6731, 6845, 7499, 7508, 7562, 7835, 8411, 8831, 9032, 9386, 9764, 9839, 11027, 11885, 14990, 19589, 20498, 21080, 22844, 24821, 25220, 26393, 27593, 29864, 29921
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 2312 is included because 123121, 323123, 723127 and 923129 are all primes.
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MATHEMATICA
| Select[ Range[ 30000 ], PrimeQ[ ToExpression[ StringInsert[ ToString[ # ], "1", {1, -1} ] ] ] && PrimeQ[ ToExpression[ StringInsert[ ToString[ # ], "3", {1, -1} ] ] ] && PrimeQ[ ToExpression[ StringInsert[ ToString[ # ], "7", {1, -1} ] ] ] && PrimeQ[ ToExpression[ StringInsert[ ToString[ # ], "9", {1, -1} ] ] ] & ]
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CROSSREFS
| Cf. A032682, A059693, A059694.
Sequence in context: A205220 A188250 A008524 * A108108 A123456 A144521
Adjacent sequences: A059674 A059675 A059676 * A059678 A059679 A059680
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KEYWORD
| base,nonn
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AUTHOR
| Harvey P. Dale (hpd1(AT)nyu.edu), Feb 05 2001
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EXTENSIONS
| More terms from Patrick De Geest (pdg(AT)worldofnumbers.com), Feb 07 2001.
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