A074876 Numbers n such that sigma(sigma(n) - phi(n)) = phi(sigma(n) + phi(n)).

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

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