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%I #17 Sep 08 2022 08:46:24
%S 5,11,13,17,29,43,47,61,67,71,73,89,101,103,107,109,127,151,181,191,
%T 197,223,227,241,251,269,277,283,317,349,359,373,397,409,421,433,457,
%U 461,467,487,521,541,569,571,631,643,647,659,673,701,709,719,733,739,751,757,769,821,857,859,881,883
%N Primes p such that 2*p-1 is a semiprime.
%H Robert Israel, <a href="/A328058/b328058.txt">Table of n, a(n) for n = 1..10000</a>
%e a(3)=13 is in the sequence because it is prime and 2*13-1=5^2 is a semiprime.
%p select(t -> isprime(t) and numtheory:-bigomega(2*t-1)=2, [2,seq(i,i=3..10000,2)]);
%t Select[Prime@ Range@ 153, PrimeOmega[2 # - 1] == 2 &] (* _Michael De Vlieger_, Oct 03 2019 *)
%o (Magma) [p: p in PrimesUpTo(1000)| &+[d[2]: d in Factorization(2*p-1)] eq 2]; // _Marius A. Burtea_, Oct 03 2019
%o (PARI) isok(p) = isprime(p) && (bigomega(2*p-1) == 2); \\ _Michel Marcus_, Oct 04 2019
%Y Cf. A000040, A001358. Includes A067756 and A162336.
%Y Cf. A086006, A234095.
%K nonn
%O 1,1
%A _J. M. Bergot_ and _Robert Israel_, Oct 03 2019