Data update

Task/Long-primes/PascalABC.NET/long-primes.pas

@@ -0,0 +1,34 @@
+function gen_primes_upto(n: integer): sequence of integer;
+begin
+  if n < 3 then exit;
+  var table := |True| * n;
+  var sqrtn := n.sqrt.Floor;
+  for var i := 2 to sqrtn do
+    if table[i] then
+      for var j := i * i to n - 1 step i do
+        table[j] := False;
+
+  yield 2;
+  for var i := 3 to n step 2 do
+    if table[i] then yield i
+end;
+
+function period(n: integer): integer;
+begin
+  var r := 1;
+  repeat
+    r := r * 10 mod n;
+    result += 1;
+  until r <= 1;
+end;
+
+begin
+  writeln('The long primes up to 500 are:');
+  var primes := Gen_primes_upto(64000).Skip(1);
+  primes.Where(x -> (x < 500) and (period(x) = x - 1)).Println;
+  writeln;
+
+  writeln('The number of long primes up to:');
+  foreach var n in |500, 1000, 2000, 4000, 8000, 16000, 32000, 64000| do
+    writeln(n:6, ' is ', primes.Where(x -> (x < n) and (period(x) = x - 1)).Count);
+end.