A348584 Numbers k such that k | A328258(k).

1, 12, 56, 180, 992, 16256, 127400, 441000, 2646000, 67100672, 325458000, 2758909440, 17179738112, 274877382656

Offset

1,2

Comments

The corresponding ratios A113184(k)/k are 1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -1, -1, ...

If p is a Mersenne exponent (A000043), then 2^p*(2^p-1) (twice an even perfect number) is a term with ratio A328258(k)/k = -1.

If there exists an odd term k, then it is a unitary multiply-perfect number (A327158), since A328258(k) = A034448(k) for an odd k.

Links

Table of n, a(n) for n=1..14.

Example

12 is a term since A328258(12) = -12 is divisible by 12.

Mathematica

f[p_, e_] := 1 - (-1)^p*(p^e); s[1] = 1; s[n_] := Times @@ f @@@ FactorInteger[n]; Select[Range[3*10^6], Divisible[s[#], #] &]

Crossrefs

The unitary version of A348583.

A139256 is a subsequence.

Cf. A000043, A034448, A327158, A328258.

Sequence in context: A212508 A331771 A009430 * A035289 A275505 A009827

Adjacent sequences: A348581 A348582 A348583 * A348585 A348586 A348587

Keyword

nonn,more

Author

Amiram Eldar, Oct 24 2021

Status

approved