Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #20 Dec 05 2024 10:47:15
%S 1,54,99,112,540,3344,4743,6720,7644,8307,11088,12852,15225,20300,
%T 22320,83160,86304,94944,129504,160208,186992,200640,205712,207264,
%U 266266,280592,331731,364941,383724,404550,441232,445050,447876,449072,454575,458052,497781
%N Numbers k such that phi(k) is equal to A008473(k).
%H Amiram Eldar, <a href="/A039779/b039779.txt">Table of n, a(n) for n = 1..866</a> (terms below 10^10)
%e phi(54) = 18, 54 = 2^1*3^3, (2+1)*(3+3) = 18.
%t Reap[For[n = 1, n < 500000, n++, If[EulerPhi[n] == Times @@ Plus @@@ FactorInteger[n], Print[n]; Sow[n]]]][[2, 1]] (* _Jean-François Alcover_, May 06 2017 *)
%o (PARI) is(k) = {my(f = factor(k)); eulerphi(f) == prod(i = 1, #f~, f[i, 1] + f[i, 2]);} \\ _Amiram Eldar_, Dec 04 2024
%Y Cf. A000010, A008473.
%K nonn
%O 1,2
%A _Olivier Gérard_