|
%I #7 Feb 22 2020 12:51:02
%S 1,3,4,5,6,8,9,10,14,17,26,28,33,38,40,44,56,62,65,70,74,78,82,98,100,
%T 110,112,122,129,130,136,138,158,164,174,176,182,186,190,194,208,210,
%U 212,220,222,230,238,242,244,246,248,250,256,257,258,278,282,284,290
%N Numbers k such that usigma(x) = k has a unique solution, where usigma(k) is the sum of unitary divisors of k (A034448).
%H Amiram Eldar, <a href="/A332739/b332739.txt">Table of n, a(n) for n = 1..10000</a>
%t usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); m = 300; v = Table[ 0, {m}]; Do[u = usigma[k]; If[u <= m, v[[u]]++], {k, 1, m}]; Position[v, _?(# == 1 &)]//Flatten
%Y Cf. A007370, A034448, A064000.
%K nonn
%O 1,2
%A _Amiram Eldar_, Feb 21 2020
|
