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Search: id:A068368
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| A068368 |
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Composite n such that sigma(2n+1)-sigma(n)=n+1. |
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+0
1
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| 16, 335, 8399, 12599, 16383, 62999, 546359, 743999, 2815199, 3046655, 3592655, 8422679, 25357439, 26356199, 29318279, 75428999, 112039199, 202417343, 226325999, 329611559, 335894159, 452921039
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Primes satisfying sigma(2p+1)-sigma(p)=p+1 are Sophie Germain primes A005384(n)
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PROGRAM
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(PARI) for(n=1, 500000000, if((sigma(2*n+1)-sigma(n)==n+1) && (!isprime(n)), print1(n, ", ")))
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CROSSREFS
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Sequence in context: A165128 A165121 A159536 this_sequence A013993 A058722 A136269
Adjacent sequences: A068365 A068366 A068367 this_sequence A068369 A068370 A068371
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KEYWORD
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easy,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 28 2002
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EXTENSIONS
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More terms from Rick L. Shepherd (rshepherd2(AT)hotmail.com), May 08 2002
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