1,2

Numbers k for which A347870(k) differs from A000035(k).

Table of n, a(n) for n=1..75.

ad[1] = 0; ad[n_] := n * Total@(Last[#]/First[#]& /@ FactorInteger[n]); Select[Range[136], Mod[ad[DivisorSigma[1, #]], 2] != Mod[#, 2] &] (* Amiram Eldar, Sep 18 2021 *)

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

Positions of ones in A347871 (the characteristic function). A347872 gives the complement.

Sequence in context: A266510 A266540 A342790 * A139759 A030292 A204231

Adjacent sequences: A347870 A347871 A347872 * A347874 A347875 A347876

nonn

Antti Karttunen, Sep 17 2021

approved