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

Author

Robert G. Wilson v, Jan 23 2002

Keywords

• nonn
• more

Comments

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

Crossrefs

Cf. A048050, A074844.

Programs

Mathematica

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

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]

Extensions

Name clarified by Sean A. Irvine, Nov 25 2023