OFFSET
0,1
COMMENTS
Does a(n) exist for every n?
LINKS
EXAMPLE
a(3) = 22100 because there are exactly 3 values x (120, 130, and 141) such that sigma(2,x) = 22100, and this property does not hold for any number smaller than 22100.
MATHEMATICA
t=Gather@ Sort@ DivisorSigma[2, Range@ 800000]; Join[{2}, Table[ Select[t, k == Length@ # &, 1][[1, 1]], {k, 8}]]
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Apr 20 2016
STATUS
approved