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A074876 Numbers n such that sigma(sigma(n) - phi(n)) = phi(sigma(n) + phi(n)). 0
4, 16, 85, 923, 6713, 8035, 8827, 10109, 19349, 21671, 30565, 31499, 41285, 116129, 154255, 269009, 282799, 312997, 362483, 477325, 486301, 498329, 525083, 607057, 609367, 714589, 995087, 1038841, 2013187, 2084785, 2088545, 2148409, 2185937 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..33.

EXAMPLE

sigma(sigma(85) - phi(85)) = sigma(108 - 64) = 84; phi(sigma(85) + phi(85)) = phi(108 + 64) = 84, so 85 is a term of the sequence.

MATHEMATICA

r = {}; Do[d = DivisorSigma[1, n]; e = EulerPhi[n]; If[DivisorSigma[1, d - e] == EulerPhi[d + e], r = Append[r, n]], {n, 1, 10^5}]; r

CROSSREFS

Sequence in context: A144882 A298012 A006681 * A238722 A184507 A165964

Adjacent sequences:  A074873 A074874 A074875 * A074877 A074878 A074879

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Sep 12 2002

EXTENSIONS

a(14)-a(33) from Donovan Johnson, Feb 17 2010

STATUS

approved

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Last modified July 5 21:00 EDT 2020. Contains 335473 sequences. (Running on oeis4.)