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 A252662 #10 Sep 08 2022 08:46:10 %S A252662 4,8,10,14,20,26,38,44,56,80,190 %N A252662 Numbers m such that 9^m - m is a semiprime. %C A252662 a(12) >= 250. - _Hugo Pfoertner_, Aug 03 2019 %H A252662 factordb.com, <a href="http://factordb.com/index.php?query=9%5E250-250">Status of 9^250-250</a>. %e A252662 4 is in this sequence because 9^4-4 = 79*83 and these two factors are prime. %e A252662 14 is in this sequence because 9^14-14 = 163*140348419969 and these two factors are prime. %t A252662 Select[Range[80], PrimeOmega[9^# - #]==2 &] %o A252662 (Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..80] | IsSemiprime(s) where s is 9^m-m]; %Y A252662 Cf. similar sequences listed in A252656. %K A252662 nonn,more,hard %O A252662 1,1 %A A252662 _Vincenzo Librandi_, Dec 22 2014 %E A252662 a(11) from _Hugo Pfoertner_, Aug 03 2019