speed up execution from 11 to 5 seconds

src/main.rs

@@ -163,7 +163,7 @@ fn main() -> anyhow::Result<()> {
         let cpu = cpu.clone();
         let results = Arc::clone(&results);
         let handle = thread::spawn(move || {
-            for n in ((1000 + cpu * 1000)..=100000).step_by(1000 + cpu * 1000) {
+            for n in ((1000 + cpu * 1000)..=100000).step_by(1000 * num_cpus) {
                 if results.read().expect("can't read results map").get(&(n as u64)).is_some() {
                     continue;
                 }