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 A353869 #10 May 09 2022 15:18:23 %S A353869 1,2,3,6,14,15,30,35,42,65,70,78,105,119,130,182,190,195,210,238,255, %T A353869 357,370,377,390,418,455,510,546,570,595,663,714,754,910,969,1045, %U A353869 1110,1118,1131,1190,1254,1326,1330,1365,1547,1558,1615,1785,1885,1887,1938,2090,2190,2261,2262,2470,2590,2639,2730 %N A353869 Squarefree numbers k such that the Carmichael function A002322(k) divides the Dedekind psi A001615(k). %C A353869 If s,t are terms, then so is lcm(s,t); in particular, if s,t are coprime, then s*t is also a term. Primitive squarefree terms are listed in A353871. %t A353869 psi[1] = 1; psi[n_] := n * Times @@ (1 + 1/Transpose[FactorInteger[n]][[1]]); Select[Range[3000], SquareFreeQ[#] && Divisible[psi[#], CarmichaelLambda[#]] &] (* _Amiram Eldar_, May 09 2022 *) %Y A353869 Intersection of A005117 and A353868. %Y A353869 Cf. A002322, A001615, A353870, A353871. %K A353869 nonn,mult %O A353869 1,2 %A A353869 _Max Alekseyev_, May 08 2022