

A247836


Primes p of the form sigma(2q1) 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
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OFFSET

1,1


COMMENTS



LINKS



EXAMPLE

Prime 13 is in sequence because there is prime 5 such that sigma(2*51) = sigma(9) = 13.


PROG

(Magma) Sort([a: p in PrimesUpTo(5000000)  IsPrime(a) where a is SumOfDivisors(2*p1)]) # corrected by Jaroslav Krizek, Nov 16 2014
(PARI) forprime(p=1, 10^9, if(isprime(sigma(2*p1)), print1(sigma(2*p1), ", "))) \\ Derek Orr, Sep 25 2014


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



