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 A242204 #17 Sep 08 2022 08:46:08 %S A242204 2,6,8,9,13,15,25,36,37,63,66,72,73,85,205,333,430 %N A242204 Numbers n such that n*4^n+1 is semiprime. %C A242204 The semiprimes of this form are: 33, 24577, 524289, 2359297, 872415233, 16106127361, 28147497671065601, 170005193383307227693057, 698910239464707491627009, ... %C A242204 a(18) >= 547. - _Hugo Pfoertner_, Aug 05 2019 %H A242204 factordb.com, <a href="http://factordb.com/index.php?query=547*4%5E547%2B1">Status of 547*4^547+1</a>. %t A242204 Select[Range[120], PrimeOmega[# 4^# + 1] == 2 &] %o A242204 (Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [n: n in [1..110] | IsSemiprime(s) where s is n*4^n+1]; %Y A242204 Cf. similar sequences listed in A242203. %Y A242204 Cf. A007646, A050915. %K A242204 nonn,more,hard %O A242204 1,1 %A A242204 _Vincenzo Librandi_, May 10 2014 %E A242204 a(15)-a(17) from _Luke March_, Aug 13 2015