A060662 Sigma(x) = n has exactly six solutions.

168, 252, 288, 384, 768, 1248, 1584, 1860, 2052, 2480, 2904, 3906, 3968, 4116, 4176, 4224, 4256, 4284, 4392, 4416, 4620, 5824, 5850, 5856, 5928, 6084, 6192, 6216, 6600, 6636, 6660, 6888, 6944, 7104, 7182, 7308, 7840, 7992, 8184, 8976, 9114, 9480, 9856

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

168 = sigma(60) = sigma(78) = sigma(92) = sigma(123) = sigma(143) = sigma(167).

Maple

N:= 10^4: # for terms <= N
V:= Vector(N):
for n from 1 to N-1 do
 s:= numtheory:-sigma(n);
 if s <= N then V[s]:= V[s]+1 fi
od:
select(t -> V[t]=6, [$1..N]); # Robert Israel, Nov 21 2019

Mathematica

a = Table[ 0, {10000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 10001, a[ [ s ] ]++ ], {n, 1, 10000} ]; Select[ Range[ 10000 ], a[ [ # ] ] == 6 & ]

Crossrefs

Cf. A007370, A007371, A007372.

Sequence in context: A117529 A338605 A196591 * A171256 A059463 A302365

Adjacent sequences: A060659 A060660 A060661 * A060663 A060664 A060665

Keyword

nonn

Author

Robert G. Wilson v, Apr 18 2001

Status

approved