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 A247836 Primes p of the form sigma(2q-1) where q is a prime. 2
 13, 31, 2801, 3541, 5113, 10303, 17293, 30941, 88741, 292561, 732541, 1191373, 1395943, 2922391, 3281533, 7450171, 7781311, 12190573, 15916111, 22292563, 28792661, 67757593, 93886411, 103052953, 112137511, 124802413, 135059263, 181427431 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Subsequence of A247837. LINKS Table of n, a(n) for n=1..28. EXAMPLE Prime 13 is in sequence because there is prime 5 such that sigma(2*5-1) = sigma(9) = 13. PROG (Magma) Sort([a: p in PrimesUpTo(5000000) | IsPrime(a) where a is SumOfDivisors(2*p-1)]) # corrected by Jaroslav Krizek, Nov 16 2014 (PARI) forprime(p=1, 10^9, if(isprime(sigma(2*p-1)), print1(sigma(2*p-1), ", "))) \\ Derek Orr, Sep 25 2014 CROSSREFS Cf. A000203, A247837, A247820. Sequence in context: A227172 A180757 A214488 * A159670 A238736 A087511 Adjacent sequences: A247833 A247834 A247835 * A247837 A247838 A247839 KEYWORD nonn AUTHOR Jaroslav Krizek, Sep 24 2014 STATUS approved

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Last modified May 21 22:16 EDT 2024. Contains 372741 sequences. (Running on oeis4.)