OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
MATHEMATICA
Select[Range[20000], CompositeQ[#] && PowerMod[#, DivisorSigma[0, #]/2, DivisorSigma[1, #]] == # &] (* Amiram Eldar, Mar 22 2024 *)
PROG
(PARI) is1(n) = my(f = factor(n), s = sigma(f), d = numdiv(f)); if(d%2, Mod(sqrtint(n), s)^d, Mod(n, s)^(d/2)) == n;
is(n) = n > 1 && !isprime(n) && is1(n); \\ Amiram Eldar, Mar 22 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Mar 17 2011
EXTENSIONS
More terms from Amiram Eldar, Mar 22 2024
STATUS
approved