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 A109831 #7 Feb 16 2025 08:32:58 %S A109831 1,1,2,2,1,2,2,3,4,2,1,3,3,2,4,3,2,2,2,2,3,3,2,3,3,3,3,2,3,4,4,2,3,3, %T A109831 3,5,3,3,4,2,3,3,3,4,3,2,3,4,3,3,3,3,4,5,3,3,4,2,3,4,4,3,5,3,3,3,2,3, %U A109831 3,5,3,3,4,2,3,4,4,3,3,3,4,3,3,3,4,4,3,3,5,3,4,3,3,2,3,5,4,3,3,3,2,3 %N A109831 Greatest number of primes < prime(n) forming an arithmetic progression such that also prime(n) is a term. %C A109831 a(n) = (A000040(n) - A109833(n)) / A109832(n). %H A109831 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimeArithmeticProgression.html">Prime Arithmetic Progression</a> %H A109831 <a href="/index/Pri#primes_AP">Index entries for sequences related to primes in arithmetic progressions</a> %K A109831 nonn %O A109831 2,3 %A A109831 _Reinhard Zumkeller_, Jul 04 2005