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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
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OFFSET
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1,1
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COMMENTS
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Primes satisfying sigma(2p+1)-sigma(p)=p+1 are Sophie Germain primes A005384(n)
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LINKS
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PROG
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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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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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