A107654 Numbers k such that phi(sum of the proper divisors of k) = k.

52416, 435456, 1713600, 6407424, 9067520, 62000640, 535392000, 46367354880

Offset

1,1

Comments

241287413760 and 6094936793088000 are also terms. - Donovan Johnson, Aug 08 2012

Links

Table of n, a(n) for n=1..8.

Example

62000640 is in the sequence because sigma(62000640)-62000640 = 187545888 and phi(187545888) = 62000640.

Mathematica

Do[If[n == EulerPhi[DivisorSigma[1, n]-n], Print[n]], {n, 65000000}]

Prog

(PARI) isok(k) = eulerphi(sigma(k)-k) == k; \\ Michel Marcus, Oct 31 2025

Crossrefs

Cf. A000010, A001065.

Sequence in context: A191303 A291869 A186849 * A345611 A346328 A345620

Adjacent sequences: A107651 A107652 A107653 * A107655 A107656 A107657

Keyword

nonn,more

Author

Farideh Firoozbakht, May 26 2005

Extensions

a(7) from Donovan Johnson, Oct 12 2008

a(8) from Donovan Johnson, Aug 08 2012

Name edited by Michel Marcus, Oct 31 2025

Status

approved