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%I #3 Mar 30 2012 17:30:31
%S 576,1296,2976,3168,3648,3720,4788,4896,5544,6300,9000,9840,10656,
%T 11808,12528,13020,13320,14760,15456,16740,17920,18288,18576,19344,
%U 19840,20400,21280,22800,23296,24300,26712,26928,27552,27936,28392
%N Numbers n such that sigma (x) = n has exactly 11 solutions.
%e 576 = sigma(210) = sigma(282) = sigma(310) = sigma(322) = sigma(345) = sigma(357) = sigma(382) = sigma(385) = sigma(497) = sigma(517) = sigma(527).
%t a = Table[ 0, {30000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 30001, a[ [ s ] ]++ ], {n, 1, 30000} ]; Select[ Range[ 30000 ], a[ [ # ] ] == 11 & ]
%Y Cf. A007370, A007371, A007372.
%K nonn
%O 1,1
%A _Robert G. Wilson v_, Apr 18 2001
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