A353680 a(n) = 1 if n is odd and phi(sigma(n)) is equal to phi(n), otherwise 0.

1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0

Offset

1

Links

Antti Karttunen, Table of n, a(n) for n = 1..100000

Index entries for characteristic functions

Index entries for sequences related to sigma(n)

Formula

a(n) = A000035(n) * A353637(n).

Mathematica

a[n_] := Boole[OddQ[n] && EulerPhi[n] == EulerPhi[DivisorSigma[1, n]]]; Array[a, 100] (* Amiram Eldar, May 06 2022 *)

Prog

(PARI) A353680(n) = ((n%2) && (eulerphi(sigma(n))==eulerphi(n)));

Crossrefs

Characteristic function of A353679.

Cf. A000010, A000035, A000203, A062401, A353637.

Sequence in context: A014061 A014053 A186719 * A353637 A014037 A016419

Adjacent sequences: A353677 A353678 A353679 * A353681 A353682 A353683

Keyword

nonn

Author

Antti Karttunen, May 06 2022

Status

approved