A353637 a(n) = 1 if 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, 1, 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, 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, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 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) = 1 iff A353636(n) is zero, otherwise 0.

a(n) = A353682(n) - A353681(n).

a(n) = [A000010(n) == A062401(n)], where [ ] is the Iverson bracket.

a(n) = [1 == A353644(n)] * [1 == A353646(n)].

Mathematica

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

Prog

(PARI) A353637(n) = (eulerphi(sigma(n))==eulerphi(n));

Crossrefs

Characteristic function of A006872.

Cf. A000010, A000203, A062401, A353636, A353644, A353646, A353680, A353681, A353682.

Sequence in context: A014053 A186719 A353680 * A014037 A016419 A016391

Adjacent sequences: A353634 A353635 A353636 * A353638 A353639 A353640

Keyword

nonn

Author

Antti Karttunen, May 04 2022

Status

approved