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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

%I #9 Oct 15 2013 22:31:53

%S 0,3,18,0,14,0,88,1800,116,196,9801,377,2881,1189,711,989,3596,477,

%T 6901,5203,8473,9179,3956,7067,6439,27709,41309,10763,27117,20569,

%U 10207,69091,4976,15376,114953,18650,204469,37225,16279,130300,74450,10877

%N 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.

%C A solution is not possible for a(1), a(4) and a(6). - _Donovan Johnson_, Feb 28 2013

%H Donovan Johnson, <a href="/A082056/b082056.txt">Table of n, a(n) for n = 1..1000</a>

%t 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

%Y Cf. A000203, A000010, A082054, A082055.

%K nonn

%O 1,2

%A _Labos Elemer_, Apr 03 2003

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Last modified March 29 05:48 EDT 2024. Contains 371265 sequences. (Running on oeis4.)