A347872 Numbers k such that k and A003415(sigma(k)) have the same parity.

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

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