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A353681
a(n) = 1 if phi(sigma(n)) > phi(n), otherwise 0.
6
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
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.
Sequence in context: A113217 A189219 A189008 * A285515 A190204 A189028
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 06 2022
STATUS
approved