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A069690
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Primes that yield another prime on placing a 9 on both sides (as leading and trailing digits).
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3
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2, 19, 23, 31, 41, 43, 47, 53, 61, 67, 71, 73, 83, 101, 107, 109, 113, 149, 163, 193, 211, 239, 241, 263, 269, 277, 313, 317, 331, 347, 373, 397, 409, 421, 439, 443, 499, 521, 523, 541, 547, 607, 617, 619, 641, 647, 673, 677, 757, 787, 829, 863, 877, 907, 911
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 241 belongs to this sequence as 92419 is also a prime.
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MATHEMATICA
| Select[ Range[2000], PrimeQ[ # ] && PrimeQ[ FromDigits[ Insert[ IntegerDigits[ # ], 9, {{1}, {-1}}]]] &]
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CROSSREFS
| Cf. A069687, A069688 & A069689.
Sequence in context: A019348 A155025 A191068 * A037003 A105907 A018696
Adjacent sequences: A069687 A069688 A069689 * A069691 A069692 A069693
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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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