This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A367947 #11 Jan 08 2024 16:47:39 %S A367947 6,9,14,15,21,26,33,35,39,51,65,69,74,86,95,111,119,134,141,146,155, %T A367947 158,183,194,209,215,219,221,249,254,278,299,303,309,321,323,326,329, %U A367947 341,371,386,393,398,411,413,453,473,485,515,519,543,545,551,554,581,611,614 %N A367947 Semiprimes s such that 2*s+1 is prime. %F A367947 a(n) = (A063640(n) - 1)/2. - _Hugo Pfoertner_, Dec 05 2023 %o A367947 (Python) %o A367947 import sympy as sp %o A367947 l = [] %o A367947 for i in range(620): %o A367947 if (sum(sp.factorint(i).values()) == 2) and sp.isprime(2*i+1): %o A367947 l.append(i) %o A367947 print(l) %o A367947 (PARI) isok(s) = (bigomega(s)==2) && isprime(2*s+1); \\ _Michel Marcus_, Dec 06 2023 %Y A367947 Intersection of A001358 and A005097. %Y A367947 Cf. A063640. %K A367947 nonn %O A367947 1,1 %A A367947 _Alexandre Herrera_, Dec 05 2023