A278054 Primes p of the form sigma(2^(q+1)) for some prime q.
31, 127, 8191, 524287, 2147483647, 2305843009213693951
Offset: 1
Keywords
Examples
8191 = sigma(2^(q+1)) for prime q = 11.
Links
- Jaroslav Krizek, Table of n, a(n) for n = 1..7
Programs
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Magma
[SumOfDivisors(2^(n+1)): n in [1..1000] | IsPrime(n) and IsPrime(SumOfDivisors(2^(n+1)))];
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Mathematica
Select[DivisorSigma[1, 2^(# + 1)] & /@ Prime@ Range@ 120, PrimeQ] (* Michael De Vlieger, Nov 10 2016 *)
Comments