The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A107654 Numbers n such that if sum of the proper divisors of n is equal to m then n = phi(m). 1
 52416, 435456, 1713600, 6407424, 9067520, 62000640, 535392000, 46367354880 (list; graph; refs; listen; history; text; internal format)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 28 18:27 EDT 2024. Contains 372918 sequences. (Running on oeis4.)