Initial data commit

Task/Pells-equation/Python/pells-equation.py

@@ -0,0 +1,22 @@
+import math
+
+def solvePell(n):
+    x = int(math.sqrt(n))
+    y, z, r = x, 1, x << 1
+    e1, e2 = 1, 0
+    f1, f2 = 0, 1
+    while True:
+        y = r * z - y
+        z = (n - y * y) // z
+        r = (x + y) // z
+
+        e1, e2 = e2, e1 + e2 * r
+        f1, f2 = f2, f1 + f2 * r
+
+        a, b = f2 * x + e2, f2
+        if a * a - n * b * b == 1:
+            return a, b
+
+for n in [61, 109, 181, 277]:
+    x, y = solvePell(n)
+    print("x^2 - %3d * y^2 = 1 for x = %27d and y = %25d" % (n, x, y))