OFFSET
1,2
COMMENTS
Almost all terms are squares.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
FORMULA
MATHEMATICA
f[p_, e_] := (p^(e+1)-1)*(p^e+1)/(p-1)/(p^e-1)^2; ratio[1] = 1; ratio[n_] := Times @@ (f @@@ FactorInteger[n]); Select[ratio /@ Range[10^5], IntegerQ] (* Amiram Eldar, Dec 11 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Yasutoshi Kohmoto, Oct 23 2006
EXTENSIONS
More terms from Amiram Eldar, Dec 11 2019
STATUS
approved