Update sol1.py

Author: MaximSmolskiy

Diff for: project_euler/problem_136/sol1.py

@@ -3,28 +3,29 @@
 
 Singleton Difference
 
+The positive integers, x, y, and z, are consecutive terms of an arithmetic progression.
+Given that n is a positive integer, the equation, x^2 - y^2 - z^2 = n, has exactly one solution when n = 20:
+                                    13^2 - 10^2 - 7^2 = 20.
+
+In fact there are twenty-five values of n below one hundred for which the equation has a unique solution.
+
+How many values of n less than fifty million have exactly one solution?
+
 By change of variables
 
 x = y + delta
 z = y - delta
 
 The expression can be rewritten:
 
-x^2 - y^2 - z^2 = y*(4*delta - y) = n
+x^2 - y^2 - z^2 = y * (4 * delta - y) = n
 
 The algorithm loops over delta and y, which is restricted in upper and lower limits,
 to count how many solutions each n has.
 In the end it is counted how many n's have one solution.
-
-
->>> solution(100)
-25
 """
 
-N = 50000000
-
-
-def solution(n_limit: int = N) -> int:
+def solution(n_limit: int = 50 * 10**6) -> int:
     """
     Define n count list and loop over delta, y to get the counts, then check
     which n has count == 1.
@@ -33,6 +34,8 @@ def solution(n_limit: int = N) -> int:
     0
     >>> solution(10)
     2
+    >>> solution(100)
+    25
     >>> solution(110)
     26
     """