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Search: id:A128825
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| A128825 |
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Primes p such that q = p+d (with d >= 6) is the next prime and both p and q are Sophie Germain primes. |
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1
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| 23, 83, 173, 233, 653, 1013, 1223, 1499, 1889, 2063, 2393, 2543, 2693, 2963, 3803, 4373, 5039, 6101, 6263, 6323, 6491, 7079, 7643, 7883, 9473, 10691, 13883, 14153, 14303, 15161, 16811, 17669, 19553, 19913, 20753, 20759, 21701, 22259, 22343
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Sophie Germain primes are primes p such that 2*p+1 is also prime.
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EXAMPLE
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653 and 659 are consecutive primes with difference 6. 2*653+1 = 1307 is prime and 2*659 + 1 = 1319 is prime. Hence 653 is a term.
1499 and 1511 are consecutive primes with difference 12 >=6. 2*1499+1 = 2999 is prime and 2*1511+1 = 3023 is prime. Hence 1499 is a term.
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PROGRAM
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(MAGMA) [ p : p in PrimesUpTo(25000) | d ge 6 and IsPrime(2*p+1) and IsPrime(2*(p+d)+1) where d is NextPrime(p)-p ]; /* Klaus Brockhaus, Apr 15 2007 */
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CROSSREFS
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Cf. A005384 (Sophie Germain primes).
Sequence in context: A116659 A139940 A052073 this_sequence A142790 A104068 A060456
Adjacent sequences: A128822 A128823 A128824 this_sequence A128826 A128827 A128828
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KEYWORD
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nonn
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AUTHOR
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J. M. Bergot (thekingfishb(AT)yahoo.ca), Apr 12 2007
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EXTENSIONS
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Edited, corrected and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Apr 15 2007
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