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%I #19 Jan 06 2020 18:10:24
%S 1,2,3,4,6,7,8,12,14,16,24,28,31,48,56,62,112,124,127,248,254,256,496,
%T 508,768,1016,1792,2032,7936,8191,16382,30240,32512,32764,65528,65536,
%U 131056,131071,196608,262142,458752,524284,524287,1048568,1048574,2031616
%N Numbers k such that uphi(usigma(k)) = k where usigma is the sum of unitary divisors of k (A034448) and uphi is the unitary totient function (A047994).
%H Amiram Eldar, <a href="/A329855/b329855.txt">Table of n, a(n) for n = 1..74</a> (terms below 5*10^10)
%e 3 is in the sequence since uphi(usigma(3)) = uphi(4) = 3.
%t usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); uphi[1] = 1; uphi[n_] := Times @@ (-1 + Power @@@ FactorInteger[n]); Select[Range[10^4], uphi[usigma[#]] == # &]
%Y The unitary version of A001229.
%Y Cf. A034448, A047994.
%K nonn
%O 1,2
%A _Amiram Eldar_, Nov 22 2019
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