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