iscarmichael(n)=
{
k=1;\
if(isprime(n)==1,k=0,\
  for(x=1,n,\
    if(gcd(x,n)==1&&k==1,\
      if(x^(n-1)%n==1,,k=0),\
    )\
  )\
);k;
}

addhelp(iscarmichael , "iscarmichael(x): true(1) if x is a Carmichael number, false(0) if not.")

printp("iscarmichael(x): true(1) if x is a Carmichael number, false(0) if not.")