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A337189
Numbers k such that k divides A340180(k).
1
1, 2, 3, 7, 61, 75, 104, 2097, 3304, 7320, 42104, 280586
OFFSET
1,2
EXAMPLE
a(4) = 61 is a term because A340180(61) = 671 = 11*61.
MAPLE
f := proc(n)
local t, s, k;
s := numtheory:-sigma(n);
t := 0;
for k to n - 1 do if igcd(n, k) = 1 then t := t + (s mod k) end if
end do;
t
end proc:
select(t -> f(t) mod t = 0, [$1..10000]);
MATHEMATICA
f[n_] := Mod[DivisorSigma[1, n], Select[Range[n-1], CoprimeQ[#, n]&]] // Total;
Select[Range[300000], If[Divisible[f[#], #], Print[#]; True, False]&] (* Jean-François Alcover, Jan 31 2021 *)
CROSSREFS
Cf. A340180.
Sequence in context: A156585 A354744 A299923 * A087358 A255357 A270002
KEYWORD
nonn,more
AUTHOR
J. M. Bergot and Robert Israel, Jan 29 2021
EXTENSIONS
a(12) from Jean-François Alcover, Feb 01 2021
STATUS
approved