OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MAPLE
isA320514 := n -> sigma(sigma(n)) < 2*n+1:
select(isA320514, [$1..1000]);
MATHEMATICA
Select[Range[1000], DivisorSigma[1, DivisorSigma[1, #]] < 2*# + 1 &] (* Vaclav Kotesovec, Oct 14 2018 *)
PROG
(PARI) isok(n) = sigma(sigma(n)) < 2*n + 1; \\ Michel Marcus, Oct 14 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Oct 14 2018
STATUS
approved