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Numbers n such that sigma(n) = n-th composite number.
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%I #10 Jul 14 2013 09:15:06

%S 6,8,10,14,27,39,51,57,745,755,7091,268243,439681,3271489,33559819,

%T 74138989,80194627,179405777,1131818923,1170569879,1324475807,

%U 1324478657,51086967247,72229691441,72229691533,72229691993,72229693511

%N Numbers n such that sigma(n) = n-th composite number.

%o (PARI) isok(n) = (sigma(n) == A002808(n)) \\ (see script there). _Michel Marcus_, Jul 14 2013

%Y Cf. A002808, A000203.

%K nonn

%O 1,1

%A _Naohiro Nomoto_

%E a(15)-a(22) from _Donovan Johnson_, Apr 03 2008

%E a(23)-a(27) from _Donovan Johnson_, Oct 24 2010