A066924 Nonprime numbers n such that the GCD of n and the Chowla's function of n (A048050) is >= n/3.

1, 4, 9, 36, 345, 6489, 88473

Offset

1,2

Comments

No more terms below 10^9. - Amiram Eldar, Aug 28 2019

Links

Table of n, a(n) for n=1..7.

Mathematica

Select[ Range[ 10^7 ], GCD[ #, DivisorSigma[ 1, # ] - # - 1 ] >= #/3 && !PrimeQ[ # ] & ]

Prog

(PARI) f(n) = if(n>1, sigma(n)-n-1, 0); \\ A048050
isok(n) = !isprime(n) && gcd(n, f(n)) >= n/3; \\ Michel Marcus, Aug 28 2019 [Corrected by Sean A. Irvine, Nov 25 2023]

Crossrefs

Cf. A048050, A074844.

Sequence in context: A077211 A073977 A055872 * A251689 A249101 A289157

Adjacent sequences: A066921 A066922 A066923 * A066925 A066926 A066927

Keyword

nonn,more

Author

Robert G. Wilson v, Jan 23 2002

Extensions

Name clarified by Sean A. Irvine, Nov 25 2023

Status

approved