A374134 a(n) = 1 if 2*phi(n) > n, otherwise 0, where phi is Euler's totient function phi, A000010.

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

Offset

1

Links

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

Index entries for characteristic functions

Formula

a(n) = [A083254(n) > 0], where [ ] is the Iverson bracket.

a(2*k) = 0 for k >= 1. - Paolo Xausa, Jul 08 2024

Mathematica

Array[Boole[2*EulerPhi[#] > #] &, 100] (* Paolo Xausa, Jul 08 2024 *)

Prog

(PARI) A374134(n) = ((2*eulerphi(n))>n);
(Python)
from sympy import totient
def A374134(n): return int(totient(n)<<1>n) # Chai Wah Wu, Oct 27 2024

Crossrefs

Characteristic function of A089684.

Cf. A000010, A083254, A318874 (inverse Möbius transform), A323170.

Differs from A000035 first at n=105, where a(105) = 0, while A000035(105) = 1.

Differs from A374136 first at n=255, where a(255) = 1, while A374136(255) = 0.

Sequence in context: A015757 A059841 A056594 * A374136 A166698 A250299

Adjacent sequences: A374131 A374132 A374133 * A374135 A374136 A374137

Keyword

nonn

Author

Antti Karttunen, Jul 06 2024

Status

approved