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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
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
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

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