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 A250214 #27 Feb 16 2025 08:33:24 %S A250214 0,0,0,0,0,0,0,1,0,0,1,1,0,1,1,0,1,1,2,1,0,1,0,0,0,2,1,0,0,0,0,1,1,1, %T A250214 2,0,2,0,0,0,0,0,0,1,0,0,0,1,0,0,1,0,2,1,1,2,0,1,1,0,1,1,3,3,0,0,0,0, %U A250214 1,2,3,1,0,1,3,0,1,0,1,1,1,1,0,2,0,0,0,0,2,2,2,0,0,4,0,0,1,0,1,2,2,1,2,0,1,3,3,1,0,0,1,1,3,3,2,0,0,3,1,1 %N A250214 Number of values of k such that prime(n) divides A241601(k). %C A250214 a(n) is called the weak irregular index of n-th prime, that is, the Bernoulli irregular index + Euler irregular index. %C A250214 Prime(n) is a regular prime if and only if a(n) = 0. %C A250214 Does every natural number appear in this sequence? For example, for the primes 491 and 1151, a(94) = a(190) = 4. (491 and 1151 are the only primes below 1800 with weak irregular index 4 or more.) However, does a(n) have a limit? %H A250214 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IrregularPair.html">Irregular Pair</a> %e A250214 a(8) = 1 since the 8th prime is 19, which divides A241601(11). %e A250214 a(13) = 0 since the 13th prime is 41, a regular prime. %e A250214 a(19) = 2 since the 19th prime is 67, which divides both A241601(27) and A241601(58). %Y A250214 Cf. A091888, A091887, A250216, A000928, A120337, A128197, A250213. %K A250214 nonn %O A250214 1,19 %A A250214 _Eric Chen_, Dec 26 2014