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%I #11 Jan 08 2024 16:47:39
%S 6,9,14,15,21,26,33,35,39,51,65,69,74,86,95,111,119,134,141,146,155,
%T 158,183,194,209,215,219,221,249,254,278,299,303,309,321,323,326,329,
%U 341,371,386,393,398,411,413,453,473,485,515,519,543,545,551,554,581,611,614
%N Semiprimes s such that 2*s+1 is prime.
%F a(n) = (A063640(n) - 1)/2. - _Hugo Pfoertner_, Dec 05 2023
%o (Python)
%o import sympy as sp
%o l = []
%o for i in range(620):
%o if (sum(sp.factorint(i).values()) == 2) and sp.isprime(2*i+1):
%o l.append(i)
%o print(l)
%o (PARI) isok(s) = (bigomega(s)==2) && isprime(2*s+1); \\ _Michel Marcus_, Dec 06 2023
%Y Intersection of A001358 and A005097.
%Y Cf. A063640.
%K nonn
%O 1,1
%A _Alexandre Herrera_, Dec 05 2023