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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
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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; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Primes satisfying sigma(2p+1)-sigma(p)=p+1 are Sophie Germain primes A005384(n)
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PROG
| (PARI) for(n=1, 500000000, if((sigma(2*n+1)-sigma(n)==n+1) && (!isprime(n)), print1(n, ", ")))
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CROSSREFS
| Sequence in context: A165121 A159536 A176128 * A013993 A058722 A173906
Adjacent sequences: A068365 A068366 A068367 * A068369 A068370 A068371
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 28 2002
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EXTENSIONS
| More terms from Rick L. Shepherd (rshepherd2(AT)hotmail.com), May 08 2002
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