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 A242271 #16 Sep 08 2022 08:46:08 %S A242271 1,2,3,9,24,32,35,51,75,234,243,392,417,472 %N A242271 Numbers n such that n*8^n+1 is semiprime. %C A242271 The semiprimes of this form are: 9, 129, 1537, 1207959553, 113336795588871485128705, 2535301200456458802993406410753, ... %C A242271 a(15) >= 483. - _Hugo Pfoertner_, Aug 05 2019 %H A242271 factordb.com, <a href="http://factordb.com/index.php?query=8%5E483*483%2B1">Status of 483*8^483+1</a>. %t A242271 Select[Range[80], PrimeOmega[# 8^# + 1] == 2 &] %o A242271 (Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [n: n in [1..80] | IsSemiprime(s) where s is n*8^n+1]; %Y A242271 Cf. similar sequences listed in A242203. %Y A242271 Cf. A064746, A242178. %K A242271 nonn,more,hard %O A242271 1,2 %A A242271 _Vincenzo Librandi_, May 10 2014 %E A242271 a(10)-a(14) from _Hugo Pfoertner_ and _Daniel Suteu_, Aug 05 2019