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A241648 Numbers m such that the GCD of the x's that satisfy sigma(x)=m is 3. 5
4, 124, 320, 392, 416, 800, 1352, 1520, 2912, 2960, 3536, 3872, 5720, 5936, 6320, 7112, 8216, 9176, 9912, 10472, 11816, 12152, 12896, 13280, 14960, 15176, 16080, 16400, 16536, 18032, 18392, 18560, 19136, 19880, 20000, 21632, 21680, 21920, 22736, 23120, 23816 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..850

EXAMPLE

We have sigma(48)=sigma(75)=124, and gcd(48, 75) = 3, hence 124 is in the sequence.

Likewise, we have sigma(x)=2912 for x=[1116, 1236, 1701, 2007, 2181], with gcd 3.

MAPLE

N:= 10^5: # for terms <= N

V:= Vector(N):

for x from 1 to N do

  s:= numtheory:-sigma(x);

  if s <= N then

    if V[s] = 0 then V[s]:= x

    else V[s]:= igcd(V[s], x)

    fi

  fi

od: select(t -> V[t]=3, [$1..N]); # Robert Israel, Aug 18 2019

CROSSREFS

Cf. A000203, A240667, A241625, A241646, A241647, A241648, A241649, A241650.

Sequence in context: A263550 A232592 A005936 * A197779 A197610 A090082

Adjacent sequences:  A241645 A241646 A241647 * A241649 A241650 A241651

KEYWORD

nonn

AUTHOR

Michel Marcus, Apr 26 2014

STATUS

approved

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Last modified August 14 05:20 EDT 2022. Contains 356110 sequences. (Running on oeis4.)