A082056 Least x = a(n) such that sum of common prime divisors (without multiplicity) of sigma(x) and phi(x) equals n, or 0 if such number (apparently) does not exist.

0, 3, 18, 0, 14, 0, 88, 1800, 116, 196, 9801, 377, 2881, 1189, 711, 989, 3596, 477, 6901, 5203, 8473, 9179, 3956, 7067, 6439, 27709, 41309, 10763, 27117, 20569, 10207, 69091, 4976, 15376, 114953, 18650, 204469, 37225, 16279, 130300, 74450, 10877

Offset: 1

Author

Labos Elemer, Apr 03 2003

Keywords

• nonn

Comments

A solution is not possible for a(1), a(4) and a(6). - Donovan Johnson, Feb 28 2013

Links

• Donovan Johnson, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000203, A000010, A082054, A082055.

Programs

Mathematica

ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] t=Table[0, {100}]; Do[s=Apply[Plus, Intersection [ba[EulerPhi[n]], ba[DivisorSigma[1, n]]]]; If[s<101&&t[[s]]\[Equal]0, t[[s]]=n], {n, 2, 1000000}]; t