OFFSET
1,12
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
Size of set {x; usigma(x)=n}.
EXAMPLE
usigma(x)=288, invusigma(288)={138,154,165,168,213,235,248,253}, so a(288)=8, the number of all terms in the inverse set.
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Sep 05 2001
STATUS
approved