|
|
A070172
|
|
Smallest k such that sigma(k) >= n.
|
|
3
|
|
|
1, 2, 2, 3, 4, 4, 4, 6, 6, 6, 6, 6, 8, 8, 8, 10, 10, 10, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 16, 16, 16, 18, 18, 18, 18, 18, 18, 18, 18, 20, 20, 20, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 36, 36
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
It seems that lim n -> infinity a(n)/n*log(log(n))=C=0.6...
|
|
MATHEMATICA
|
nn=80; With[{s=Table[{n, DivisorSigma[1, n]}, {n, nn}]}, Transpose[ Flatten[ Table[ Select[s, #[[2]]>=i&, 1], {i, nn}], 1]][[1]]] (* Harvey P. Dale, Dec 28 2013 *)
|
|
PROG
|
(PARI) for(n=1, 150, s=1; while(sigma(s)<n, s++); print1(s, ", "))
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|