A353681 a(n) = 1 if phi(sigma(n)) > phi(n), otherwise 0.

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

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) = [A353636(n) > 0], where [ ] is the Iverson bracket.

a(n) = A353682(n) - A353637(n).

Mathematica

Table[Boole[EulerPhi[DivisorSigma[1, n]] > EulerPhi[n]], {n, 1, 120}] (* Amiram Eldar, May 06 2022 *)

Prog

(PARI) A353681(n) = (eulerphi(sigma(n))>eulerphi(n));

Crossrefs

Characteristic function of A353683, while its complement A353685 gives the positions of zeros.

Cf. A000010, A000203, A062401, A353636, A353637, A353682.

Sequence in context: A113217 A189219 A189008 * A285515 A190204 A189028

Adjacent sequences: A353678 A353679 A353680 * A353682 A353683 A353684

Keyword

nonn

Author

Antti Karttunen, May 06 2022

Status

approved