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 A092558 #13 Feb 22 2022 21:25:42 %S A092558 11,23,101,167,199,347 %N A092558 Numbers k such that 2^k +- 1 are both semiprimes. %C A092558 Intersection of A092559 and A085724. %C A092558 a(7), if it exists, is at least 41519. - _Charles R Greathouse IV_, Jun 05 2013 %C A092558 2^41519 + 1 is the product of 3 and a composite number, so if a(7) exists, it exceeds 41519. - _Jon E. Schoenfield_, Feb 22 2022 %e A092558 11 is a term because 2^11 - 1 = 23*89 and 2^11 + 1 = 3*683. %o A092558 (PARI) is(n)=isprime(n) && n>7 && ispseudoprime((2^n+1)/3) && bigomega(2^n-1)==2 \\ _Charles R Greathouse IV_, Jun 05 2013 %Y A092558 Subsequence of A000040. %Y A092558 Cf. A092559, A085724, A092561, A092562. %K A092558 nonn %O A092558 1,1 %A A092558 _Zak Seidov_, Feb 27 2004 %E A092558 a(6) from _Robert G. Wilson v_, Apr 18 2006