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

1,2

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

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

Crossrefs

Cf. A000203, A000010, A082054, A082055.

Sequence in context: A162713 A161473 A208493 * A082057 A161687 A245498

Adjacent sequences: A082053 A082054 A082055 * A082057 A082058 A082059

Keyword

nonn

Author

Labos Elemer, Apr 03 2003

Status

approved