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 A337189 #25 Feb 06 2021 21:59:57 %S A337189 1,2,3,7,61,75,104,2097,3304,7320,42104,280586 %N A337189 Numbers k such that k divides A340180(k). %e A337189 a(4) = 61 is a term because A340180(61) = 671 = 11*61. %p A337189 f := proc(n) %p A337189 local t, s, k; %p A337189 s := numtheory:-sigma(n); %p A337189 t := 0; %p A337189 for k to n - 1 do if igcd(n, k) = 1 then t := t + (s mod k) end if %p A337189 end do; %p A337189 t %p A337189 end proc: %p A337189 select(t -> f(t) mod t = 0, [$1..10000]); %t A337189 f[n_] := Mod[DivisorSigma[1, n], Select[Range[n-1], CoprimeQ[#, n]&]] // Total; %t A337189 Select[Range[300000], If[Divisible[f[#], #], Print[#]; True, False]&] (* _Jean-François Alcover_, Jan 31 2021 *) %Y A337189 Cf. A340180. %K A337189 nonn,more %O A337189 1,2 %A A337189 _J. M. Bergot_ and _Robert Israel_, Jan 29 2021 %E A337189 a(12) from _Jean-François Alcover_, Feb 01 2021