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 A109909 #13 Sep 29 2024 11:56:45 %S A109909 0,0,0,2,2,1,2,1,4,1,3,2,3,2,3,2,4,3,5,1,10,1,5,5,4,2,6,3,5,3,9,4,11, %T A109909 3,5,5,5,5,14,1,6,6,7,6,11,5,8,4,15,3,13,4,10,9,6,5,11,4,12,5,13,4,12, %U A109909 4,6,11,13,4,12,6,15,12,9,4,9,5,10,8,10,3,28,7,11,15,6,9,20,7,20,6,17,5,23 %N A109909 a(n) = number of primes of the form k*(n-k)-1. %C A109909 Conjecture: a(n) > 0 for n > 3. %C A109909 Conjecture verified up to 10^9. - _Mauro Fiorentini_, Jul 23 2023 %H A109909 Pengcheng Niu and Junli Zhang, <a href="https://doi.org/10.13140/RG.2.2.16430.11848">On Two Conjectures of A. Murthy</a>, ResearchGate (2024). %Y A109909 Cf. A109904, A109905, A026728, A109907, A109908. %K A109909 nonn %O A109909 1,4 %A A109909 _Amarnath Murthy_, Jul 15 2005 %E A109909 More terms from _David Wasserman_, Aug 15 2005