|
|
A289124
|
|
Numbers n such that sigma(sigma(n))/sigma(n) > sigma(sigma(m))/sigma(m) for all m < n.
|
|
2
|
|
|
1, 2, 3, 5, 6, 14, 22, 24, 54, 88, 114, 120, 264, 312, 520, 540, 864, 1560, 3432, 4320, 8856, 9120, 10464, 20664, 21276, 32760, 36840, 52320, 92280, 106380, 170040, 185760, 201240, 417960, 613080, 1059480, 1098720, 1937880, 2213640, 2982240, 5611320, 9809280
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
Erdős proved that sigma(sigma(n))/sigma(n) is unbounded, thus this sequence is infinite.
|
|
LINKS
|
|
|
MATHEMATICA
|
a = {}; k=1; rmax = 0; While[Length[a]<40, s = DivisorSigma[1, k]; s2 = DivisorSigma[1, s]; r = s2/s; If[r > rmax, AppendTo[a, k]; rmax = r]; k++]; a
|
|
PROG
|
(PARI) r=0; forfactored(n=1, 10^10, t=sigma(sigma(n), -1); if(t>r, r=t; print1(n[1]", "))) \\ Charles R Greathouse IV, Jun 25 2017
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|