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 A109908 #14 Jul 24 2023 01:23:34
%S A109908 0,0,0,3,5,7,11,11,19,23,29,31,41,47,53,59,71,79,89,83,109,71,131,139,
%T A109908 149,167,181,191,197,223,239,251,271,263,293,307,311,359,379,383,419,
%U A109908 439,461,479,503,503,521,571,599,599,647,659,701,727,743,719,811,839
%N A109908 a(n) = greatest prime of the form k*(n-k)-1, or 0 if no such prime exists.
%C A109908 Conjecture: a(n) > 0 for n > 3.
%C A109908 Conjecture verified up to 10^9. - _Mauro Fiorentini_, Jul 23 2023
%o A109908 (PARI) { a(n)=forstep(k=n\2,1,-1,if(isprime(k*(n-k)-1),return(k*(n-k)-1)));return(0) } \\ _Max Alekseyev_, Oct 04 2005
%Y A109908 Cf. A109904, A109905, A026728, A109907, A109909.
%K A109908 nonn,easy
%O A109908 1,4
%A A109908 _Amarnath Murthy_, Jul 15 2005
%E A109908 More terms from _Max Alekseyev_, Oct 04 2005
%E A109908 Definition corrected by _David Wasserman_, Oct 28 2008