OFFSET
1,2
COMMENTS
A211656 is the sorted version of this sequence.
LINKS
EXAMPLE
a(6) = 7 because A007370(6) = 8 and there is only one solution of equation sigma(x) = 8 for x = 7.
MATHEMATICA
m = 500; v = Table[0, {m}]; Do[s = DivisorSigma[1, k]; If[s <= m , v[[s]] = If[ v[[s]] == 0, k, -1]], {k, 1, m - 1}]; Select[v, # > 0 &] (* Amiram Eldar, Jul 04 2019 *)
PROG
(Magma) [[m: m in [1..1000] | SumOfDivisors(m) eq n]: n in [1..100] | #[#[m]: m in [1..1000] | SumOfDivisors(m) eq n] eq 1]
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, May 12 2019
STATUS
approved