Data update

Task/Pells-equation/PascalABC.NET/pells-equation.pas

@@ -0,0 +1,31 @@
+function solvePell(n: integer): (biginteger, biginteger);
+begin
+  var x: biginteger := n.sqrt.floor;
+  var (y, z, r) := (x, 1bi, x shl 1);
+  var (e1, e2) := (1bi, 0bi);
+  var (f1, f2) := (0bi, 1bi);
+
+  repeat
+    y := r * z - y;
+    z := (n - y * y) div z;
+    r := (x + y) div z;
+
+    (e1, e2) := (e2, e1 + e2 * r);
+    (f1, f2) := (f2, f1 + f2 * r);
+
+    var (a, b) := (f2 * x + e2, f2);
+    if a * a - n * b * b = 1 then
+    begin
+      result := (a, b);
+      exit
+    end;
+  until false;
+end;
+
+begin
+  foreach var n in |61, 109, 181, 277| do
+  begin
+    var (x, y) := solvePell(n);
+    writeln('x² - ', n:3, ' * y² = 1 for (x, y) = (', x:21, ',',y:20, ')');
+  end;
+end.