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 A252789 #18 Sep 08 2022 08:46:10 %S A252789 7,19,39,43,87,135,147,177,223,255,403 %N A252789 Numbers m such that 4^m + m is a semiprime. %C A252789 From _Kevin P. Thompson_, Apr 26 2022: (Start) %C A252789 a(12) >= 765. %C A252789 795 and 949 are also terms in this sequence. (End) %H A252789 FactorDB, <a href="http://factordb.com/index.php?id=1100000000880425557">Status of 4^765+765</a>. %e A252789 7 is in this sequence because 4^7+7 = 37*443 and these two factors are prime. %e A252789 19 is in this sequence because 4^19+19 = 11*24988900633 and these two factors are prime. %t A252789 Select[Range[130], PrimeOmega[4^# + #]==2 &] %o A252789 (Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..130] | IsSemiprime(s) where s is 4^m+m]; %o A252789 (PARI) main(m)=select(m->bigomega(4^m + m)==2, vector(m, i, i)); \\ _Anders Hellström_, Aug 14 2015 %Y A252789 Cf. similar sequences listed in A252788. %Y A252789 Cf. A252657. %K A252789 nonn,more %O A252789 1,1 %A A252789 _Vincenzo Librandi_, Dec 24 2014 %E A252789 a(6)-a(9) from _Carl Schildkraut_, Aug 14 2015 %E A252789 a(10)-a(11) from _Kevin P. Thompson_, Apr 26 2022