OFFSET
1,2
EXAMPLE
24 is in this sequence because tau(24) = 8 and -8^2 mod 24 = 8.
MAPLE
q:= n-> (t-> irem(t^2+t, n)=0)(numtheory[tau](n)):
select(q, [$1..1000])[]; # Alois P. Heinz, Feb 26 2020
MATHEMATICA
Select[Range[1000], Divisible[(d = DivisorSigma[0, #]) + d^2, #] &] (* Amiram Eldar, Feb 26 2020 *)
PROG
(PARI) isok(m) = my(nd=numdiv(m)); Mod(-nd^2, m) == nd; \\ Michel Marcus, Feb 26 2020
CROSSREFS
KEYWORD
nonn,fini,full
AUTHOR
Juri-Stepan Gerasimov, Feb 26 2020
STATUS
approved