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A241649
Numbers m such that the GCD of the x's that satisfy sigma(x)=m is 4.
5
7, 210, 378, 630, 1904, 3570, 6188, 6510, 7154, 9296, 9800, 10220, 12446, 13664, 14378, 17654, 17780, 18536, 19110, 19376, 19530, 20034, 20580, 21266, 23240, 23310, 24150, 24584, 25298, 26754, 27930, 28938, 29106, 29610, 30380, 31640, 34146, 34230, 34664
OFFSET
1,1
LINKS
EXAMPLE
sigma(104) = sigma(116) = 210, and gcd(104, 116) = 4, hence 210 is in the sequence.
Likewise 6510 is obtained with sigma of [2600, 2900, 3464, 3716], with gcd 4.
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]=4, [$1..N]); # Robert Israel, Aug 18 2019
KEYWORD
nonn
AUTHOR
Michel Marcus, Apr 26 2014
STATUS
approved