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 A085725 #26 Mar 03 2023 19:19:05 %S A085725 6,8,9,14,18,19,21,23,26,34,36,40,48,54,76,88,105,122,135 %N A085725 Numbers k such that 1 + (product of first k primes) is a semiprime. %C A085725 See A250293 for more information. %F A085725 a(n) = primepi(A250293(n)). - _Hugo Pfoertner_, Feb 05 2021 %o A085725 (PARI) isok(k) = bigomega(1 + prod(j=1, k, prime(j))) == 2; \\ _Michel Marcus_, Mar 30 2019 %Y A085725 Cf. A001358 (semiprimes), A002110, A006862 (Euclid numbers), A250293. %K A085725 more,hard,nonn %O A085725 1,1 %A A085725 _Jason Earls_, Jul 20 2003 %E A085725 More terms from _David Wasserman_, Feb 09 2005 %E A085725 a(14)=54 from _Donovan Johnson_, Feb 21 2008 %E A085725 Offset changed to 1 by _Alois P. Heinz_, Jul 02 2015 %E A085725 a(15) added by _Daniel Suteu_, Mar 30 2019 %E A085725 a(16)-a(18) using terms of A250293 from _Hugo Pfoertner_, Feb 05 2021 %E A085725 Missing 105 inserted by _Sean A. Irvine_, Mar 03 2023