Data update

Task/Chowla-numbers/PascalABC.NET/chowla-numbers.pas

@@ -0,0 +1,54 @@
+function chowla(n: Integer): Integer;
+begin
+  result := 0;
+  var i := 2;
+  while i * i <= n do
+  begin
+    if n mod i = 0 then
+      result += i + (if i = n div i then 0 else n div i);
+    i += 1
+  end;
+end;
+
+function sieve(limit: Integer): array of Boolean;
+begin
+  result := new Boolean[limit];
+  for var i := 3 to limit div 3 step 2 do
+    if not result[i] and (chowla(i) = 0) Then
+      for var j := 3 * i to limit step 2 * i do
+        result[j] := true;
+end;
+
+begin
+  for var i := 1 To 37 do
+    WriteLn('chowla(', i, ') = ', chowla(i));
+
+  var count := 1;
+  var limit := 10_000_000;
+  var power := 100;
+  var c := sieve(limit);
+  for var i := 3 To limit Step 2 do
+  begin
+    if not c[i] Then count += 1;
+    if i = power - 1 Then begin
+      WriteLn('Count of primes up to ', power:8, ' = ', count);
+      power *= 10;
+    end;
+  end;
+
+  count := 0;
+  limit := 35_000_000;
+  var k := 2; var kk := 3;
+  while True do
+  begin
+    var p := k * kk;
+    if p > limit Then break;
+    if chowla(p) = p - 1 Then begin
+      WriteLn(p:8, ' is a number that is perfect');
+      count += 1;
+    end;
+    k := kk + 1;
+    kk += k;
+  end;
+  WriteLn('There are ', count, ' perfect numbers <= 35,000,000')
+end.