A107654 Numbers n such that if sum of the proper divisors of n is equal to m then n = phi(m).

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

Offset

1,1

Comments

Next term is greater than 65*10^6.

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}]

Crossrefs

Cf. A107653.

Sequence in context: A191303 A291869 A186849 * A345611 A346328 A345620

Adjacent sequences: A107651 A107652 A107653 * A107655 A107656 A107657

Keyword

more,nonn

Author

Farideh Firoozbakht, May 26 2005

Extensions

a(7) from Donovan Johnson, Oct 12 2008

a(8) from Donovan Johnson, Aug 08 2012

Status

approved