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 A091424 #23 Aug 31 2024 04:34:08 %S A091424 1,3,4,6,10,30,31,98,156,230,432,490,1623,1666,9324,9693 %N A091424 Numbers m such that m#*2^m + 1 is prime, where m# = A002110(m). %C A091424 1# = 2, 2# = 2*3 = 6, 3# = 2*3*5 = 30. %C A091424 No more terms < 5000. - _L. Joris Perrenet_, Mar 17 2020 %e A091424 a(1) = 1 because 1#*2^1 + 1 = 5 is prime %e A091424 a(2) = 3 because 3#*2^3 + 1 = 241 is prime %o A091424 (PARI) pp(n)=my(s=1);for(i=1,n,s=s*prime(i));return(s); %o A091424 f(n)=pp(n)*2^n +1; %o A091424 for (i=1,500,if(isprime(f(i)),print1(i, ", "))) %Y A091424 Cf. A002110, A091421. %K A091424 nonn,hard,more %O A091424 1,2 %A A091424 Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 02 2004 %E A091424 a(13)-a(14) from _Chai Wah Wu_, Dec 23 2019 %E A091424 a(15)-a(16) from _Michael S. Branicky_, Aug 31 2024