diff --git a/fullstack-cert/python-projects/letter-frequency-counter-lab/main.py b/fullstack-cert/python-projects/letter-frequency-counter-lab/main.py
new file mode 100644
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+++ b/fullstack-cert/python-projects/letter-frequency-counter-lab/main.py
@@ -0,0 +1,12 @@
+def number_pattern(n):
+    result = "1"
+    if isinstance(n, int):
+        if n > 0:
+            for i in range(2, n + 1):
+                result += f" {i}"
+            return result
+        return "Argument must be an integer greater than 0."
+    return "Argument must be an integer value."
+
+
+print(number_pattern(13))
diff --git a/fullstack-cert/python-projects/letter-frequency-counter-lab/user-stories.md b/fullstack-cert/python-projects/letter-frequency-counter-lab/user-stories.md
new file mode 100644
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+++ b/fullstack-cert/python-projects/letter-frequency-counter-lab/user-stories.md
@@ -0,0 +1,5 @@
+1. You should define a function named `number_pattern` that takes a single parameter `n` (representing a positive integer).
+1. `number_pattern` should use a `for` loop.
+1. `number_pattern(n)` should return a string with all the integers starting from 1 up to `n` (included) separated by a space. For example, `number_pattern(4)` should return the string `1 2 3 4`.
+1. If the argument passed to the function is not an integer value, the function should return `Argument must be an integer value.`.
+1. If the argument passed to the function is less than 1, the function should return `Argument must be an integer greater than 0.`.
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