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Multiply-perfect numbers k that do not have a divisor d such that sigma(d)*d = k.
1

%I #12 Sep 28 2021 19:54:59

%S 2178540,45532800,459818240,1476304896,14182439040,31998395520,

%T 43861478400,51001180160,518666803200,704575228896,13661860101120,

%U 30823866178560,181742883469056,740344994887680,796928461056000,6088728021160320,20158185857531904,212517062615531520,622286506811515392,69357059049509038080,87934476737668055040

%N Multiply-perfect numbers k that do not have a divisor d such that sigma(d)*d = k.

%C Numbers k in A007691 for which A327153(k) = 0, that are not in A327165.

%C Question: Is A323653 a subsequence of this sequence? See also conjecture in A348033.

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%t With[{s = DeleteCases[Map[ToExpression[#] &, Import["https://oeis.org/A007691/b007691.txt", "Data"]], _?(Length[#] == 0 &)][[All, -1]]}, Select[s[[1 ;; 45]], Function[k, NoneTrue[Divisors[k], # DivisorSigma[1, #] == k &]]]] (* _Michael De Vlieger_, Sep 28 2021, using b-file at A007691 *)

%Y Cf. A348031 (complement in A007691).

%Y Cf. A327153, A327165, A348033.

%K nonn

%O 1,1

%A _Antti Karttunen_, Sep 26 2021