code: function findPrimes(n) {
    var i, s, p, ans;
    s=new Array(n);
    for (i=0; i<n; i++)
      s[i]=0;
    s[0]=2;
    p=0;    //first p elements of s are primes, the rest are a sieve
    for (;s[p]<n;) {                  //s[p] is the pth prime
      for (i=s[p]*s[p]; i<n; i+=s[p]) //mark multiples of s[p]
        s[i]=1;
      p++;
      s[p]=s[p-1]+1;
      for (; s[p]<n && s[s[p]]; s[p]++); //find next prime (where s[p]==0)
    }
    ans=new Array(p);
    for (i=0; i<p; i++)
      ans[i]=s[i];
    return ans;
  }
docs: return array of all primes less than integer n