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 A029591 #48 Feb 18 2024 02:04:11
%S A029591 6,399,598,165,1886,715,148219,273,343027,231,935,3445,4681203,1547,
%T A029591 2821,1105,21098,43183,258482,27071,2117473,3059,10373,2737,690501,
%U A029591 1595,23959,42653,1621007,9331,4169135,35465,543973,14839,36941,1885,4405589,11063
%N A029591 For n>0, a(n) is the least quasi-Carmichael number to base -n, extended to n=0 with the least composite squarefree integer.
%C A029591 a(n) is the least squarefree composite integer, for which prime p | a(n) ==> p+n | a(n)+n.
%D A029591 J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 399, p. 89, Ellipses, Paris 2008.
%H A029591 Donovan Johnson, <a href="/A029591/b029591.txt">Table of n, a(n) for n = 0..250</a>
%H A029591 J.-M. De Koninck, <a href="https://bookstore.ams.org/mbk-64/103">Those fascinating numbers, Entry 399</a>, AMS, 2009.
%H A029591 <a href="/index/Ca#Carmichael">Index entries for sequences related to Carmichael numbers.</a>
%o A029591 (PARI) a(n) = {forcomposite (k=1, oo, if (issquarefree(k) && (omega(k) >= 2), my(f=factor(k)[,1]); my(ok = 1); for (j=1, #f, if ((k+n) % (f[j]+n), ok = 0; break);); if (ok, return (k));););} \\ _Michel Marcus_, Jan 09 2020
%Y A029591 Cf. A029590 (base n), A257750 (quasi-Carmichael numbers).
%K A029591 nonn
%O A029591 0,1
%A A029591 _David W. Wilson_