cp's OEIS Frontend

A250215 Least k such that the n-th weak irregular prime (A250216(n)) divides A241601(k).

%I A250215 #18 Feb 16 2025 08:33:24
%S A250215 11,23,32,13,15,44,7,27,29,19,63,24,22,43,129,130,62,75,133,84,211,
%T A250215 127,164,100,84,9,20,156,88,87,280,19,71,125,163,100,200,382,126,159,
%U A250215 240,215,196,130,94,292,141,400,86,270,222,175,389,52,45,22,592,522,20
%N A250215 Least k such that the n-th weak irregular prime (A250216(n)) divides A241601(k).
%C A250215 A prime p can divide A241601(k) for more than one k; the first few examples are as follows:
%C A250215 p      k
%C A250215 67     27, 58
%C A250215 101    63, 68
%C A250215 149    130, 147
%C A250215 157    62, 110
%C A250215 241    211, 239
%C A250215 263    100, 213
%C A250215 307    88, 91, 137
%C A250215 311    87, 193, 292
%C A250215 349    19, 257
%C A250215 353    71, 186, 300
%C A250215 etc.
%H A250215 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IrregularPair.html">Irregular Pair</a>
%e A250215 19 is the first weak irregular prime and divides A241601(11) = 50521, so a(1) = 11.
%Y A250215 Cf. A000928, A035112, A120337, A128197, A250216.
%K A250215 nonn
%O A250215 1,1
%A A250215 _Eric Chen_, Dec 26 2014
%E A250215 More terms from _Jinyuan Wang_, Feb 18 2022