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 A060664 Sigma(x) = n has exactly eight solutions. 1
 336, 432, 672, 756, 840, 1536, 1620, 1764, 1848, 2280, 2394, 2604, 2808, 3264, 4080, 4480, 4860, 5328, 6528, 6624, 7128, 8316, 8568, 8880, 10608, 11040, 11448, 12288, 12420, 12636, 13176, 13200, 13248, 13536, 13860, 14196, 14208, 14448, 14700 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE 336 = sigma(132) = sigma(140) = sigma(182) = sigma(188) = sigma(195) = sigma(249) = sigma(287) = sigma(299). MAPLE N:= 30000: # to get terms <= N V:= Vector(N): for k from 1 to N-1 do   t:= numtheory:-sigma(k);   if t <= N then V[t]:= V[t]+1 fi od: select(t -> V[t]=8, [\$1..N]); # Robert Israel, Sep 22 2019 MATHEMATICA a = Table[ 0, {20000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 20001, a[ [ s ] ]++ ], {n, 1, 20000} ]; Select[ Range[ 20000 ], a[ [ # ] ] == 8 & ] CROSSREFS Cf. A007370, A007371, A007372. Sequence in context: A137522 A090487 A289220 * A261551 A247530 A064259 Adjacent sequences:  A060661 A060662 A060663 * A060665 A060666 A060667 KEYWORD nonn AUTHOR Robert G. Wilson v, Apr 18 2001 STATUS approved

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Last modified August 3 08:10 EDT 2020. Contains 336197 sequences. (Running on oeis4.)