A074713 Numbers n such that the sum of the anti-divisors of n = phi(n).

3, 19, 131, 139, 3949, 5881, 11341, 29501, 65789, 5440591, 2471800109

Offset

1,1

Comments

See A066272 for definition of anti-divisor.

a(12) > 6*10^9. - Donovan Johnson, Feb 04 2012

Links

Table of n, a(n) for n=1..11.

Prog

(Python)
from sympy import divisors, totient
A074713 = [n for n in range(1, 10**5) if sum([2*d for d in divisors(n) if n > 2*d and n%(2*d)] + [d for d in divisors(2*n-1) if n > d >=2 and n%d] + [d for d in divisors(2*n+1) if n > d >=2 and n%d]) == totient(n)] # Chai Wah Wu, Aug 12 2014

Crossrefs

Cf. A000010, A066417.

Sequence in context: A058860 A074568 A219053 * A199484 A063395 A226459

Adjacent sequences: A074710 A074711 A074712 * A074714 A074715 A074716

Keyword

more,nonn

Author

Jason Earls, Sep 04 2002

Extensions

Offset corrected and a(10)-a(11) from Donovan Johnson, Feb 04 2012

Status

approved