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A060676 Numbers n such that sigma (x) = n has exactly 12 solutions. 0

%I #6 Jan 18 2013 10:56:59

%S 1512,1872,2352,3192,3780,4104,4560,4752,5880,6120,8160,8424,8820,

%T 11424,13056,15264,16464,16704,17160,17360,17760,18648,19680,19800,

%U 20880,22752,23616,24552,24864,27432,30336,30492,31200,32448,35328

%N Numbers n such that sigma (x) = n has exactly 12 solutions.

%e 1512 = sigma(480) = sigma(636) = sigma(736) = sigma(748) = sigma(830) = sigma(902) = sigma(1006) = sigma(1105) = sigma(1255) = sigma(1391) = sigma(1411) = sigma(1511).

%t a = Table[ 0, {50000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 50001, a[ [ s ] ]++ ], {n, 1, 50000} ]; Select[ Range[ 50000 ], a[ [ # ] ] == 12 & ]

%t Take[Sort[Transpose[Select[Tally[DivisorSigma[1,Range[100000]]],#[[2]] == 12&]][[1]]],50] (* _Harvey P. Dale_, Jan 18 2013 *)

%Y Cf. A007370, A007371, A007372.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Apr 18 2001

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Last modified March 28 12:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)