|
| |
|
|
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
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
LINKS
|
Robert Israel, Table of n, a(n) for n = 1..698
|
|
|
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
|
|
|
CROSSREFS
|
Cf. A000203, A240667, A241625, A241646, A241647, A241648, A241650.
Sequence in context: A300619 A275822 A065819 * A256288 A302107 A061028
Adjacent sequences: A241646 A241647 A241648 * A241650 A241651 A241652
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Michel Marcus, Apr 26 2014
|
|
|
STATUS
|
approved
|
| |
|
|
