A348032 - OEIS

A348032

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

2178540, 45532800, 459818240, 1476304896, 14182439040, 31998395520, 43861478400, 51001180160, 518666803200, 704575228896, 13661860101120, 30823866178560, 181742883469056, 740344994887680, 796928461056000, 6088728021160320, 20158185857531904, 212517062615531520, 622286506811515392, 69357059049509038080, 87934476737668055040

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OFFSET

1,1

COMMENTS

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

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

LINKS

Table of n, a(n) for n=1..21.

Index entries for sequences related to sigma(n)

MATHEMATICA

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 *)

CROSSREFS

Cf. A348031 (complement in A007691).

Cf. A327153, A327165, A348033.

Sequence in context: A049359 A105711 A250491 * A224580 A224581 A224588

Adjacent sequences: A348029 A348030 A348031 * A348033 A348034 A348035

KEYWORD

nonn

AUTHOR

Antti Karttunen, Sep 26 2021

STATUS

approved