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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. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 27 15:14 EST 2020. Contains 331295 sequences. (Running on oeis4.)