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A347872 Numbers k such that k and A003415(sigma(k)) have the same parity. 7
5, 6, 8, 9, 12, 13, 14, 17, 18, 22, 24, 25, 28, 29, 30, 36, 37, 38, 41, 42, 44, 45, 46, 48, 50, 53, 54, 56, 60, 61, 62, 66, 70, 73, 76, 78, 84, 86, 88, 89, 92, 94, 96, 97, 100, 101, 102, 108, 109, 110, 112, 113, 114, 117, 118, 120, 124, 126, 130, 132, 134, 137, 138, 140, 142, 144, 149, 150, 152, 153, 154, 156, 157 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers k for which A347870(k) is equal to A000035(k).

LINKS

Table of n, a(n) for n=1..73.

Index entries for sequences where odd perfect numbers must occur, if they exist at all

MATHEMATICA

ad[1] = 0; ad[n_] := n * Total@(Last[#]/First[#]& /@ FactorInteger[n]); Select[Range[157], Mod[ad[DivisorSigma[1, #]], 2] == Mod[#, 2] &] (* Amiram Eldar, Sep 18 2021 *)

CROSSREFS

Cf. A000035, A000203, A003415, A342925, A347870.

Positions of zeros in A347871. Cf. A347873 for complement.

Cf. A000396, A342922, A347874 (subsequences).

Cf. also A347883.

Sequence in context: A158698 A120174 A184817 * A191355 A337143 A047439

Adjacent sequences:  A347869 A347870 A347871 * A347873 A347874 A347875

KEYWORD

nonn

AUTHOR

Antti Karttunen, Sep 17 2021

STATUS

approved

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Last modified January 28 10:24 EST 2022. Contains 350655 sequences. (Running on oeis4.)