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%I #8 Jul 02 2019 08:42:05
%S 1,2,9,15,18,21,40,42,60,104,120,288,312,756,1023,1170,2160,2520,3024,
%T 4092,6048,6552,8184,17850,18720,29127,30690,40768,58254,79794,147312,
%U 285600,491040,507780,556920,932064,1276704,1966020,3300570,4134780,4194288,4470648
%N Sigma unitary-sigma perfect numbers: numbers m which satisfy the following equation for some integer k: sigma(usigma(m)) = k*m where usigma(m) is sum of unitary divisors of m.
%H Amiram Eldar, <a href="/A083288/b083288.txt">Table of n, a(n) for n = 1..71</a>
%e 9 is in the sequence since usigma(9) = 10 and sigma(10) = 18 = 2 * 9 is divisible by 9.
%t usigma[1]=1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); Select[ Range[10^4], Divisible[DivisorSigma[1, usigma[#]], #] & ] (* _Amiram Eldar_, Jul 02 2019 *)
%Y Cf. A000203, A045795, A034448.
%K nonn
%O 1,2
%A _Yasutoshi Kohmoto_, Jun 05 2003
%E More terms from _Amiram Eldar_, Jul 02 2019
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