diff --git a/.travis.yml b/.travis.yml
index b9c47c179..c19ae42ec 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,5 @@
 os: linux
-dist: bionic
+dist: focal
 language: python
 python: 3.8
 cache: pip
diff --git a/DIRECTORY.md b/DIRECTORY.md
index 5025fde4a..777f5d34f 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -27,6 +27,9 @@
 ## Boolean Algebra
   * [Quine Mc Cluskey](https://github.com/TheAlgorithms/Python/blob/master/boolean_algebra/quine_mc_cluskey.py)
 
+## Cellular Automata
+  * [One Dimensional](https://github.com/TheAlgorithms/Python/blob/master/cellular_automata/one_dimensional.py)
+
 ## Ciphers
   * [Affine Cipher](https://github.com/TheAlgorithms/Python/blob/master/ciphers/affine_cipher.py)
   * [Atbash](https://github.com/TheAlgorithms/Python/blob/master/ciphers/atbash.py)
@@ -148,6 +151,7 @@
   * [Index Calculation](https://github.com/TheAlgorithms/Python/blob/master/digital_image_processing/index_calculation.py)
   * Rotation
     * [Rotation](https://github.com/TheAlgorithms/Python/blob/master/digital_image_processing/rotation/rotation.py)
+  * [Sepia](https://github.com/TheAlgorithms/Python/blob/master/digital_image_processing/sepia.py)
   * [Test Digital Image Processing](https://github.com/TheAlgorithms/Python/blob/master/digital_image_processing/test_digital_image_processing.py)
 
 ## Divide And Conquer
diff --git a/cellular_automata/one_dimensional.py b/cellular_automata/one_dimensional.py
index 98d6fa25d..7819088c8 100644
--- a/cellular_automata/one_dimensional.py
+++ b/cellular_automata/one_dimensional.py
@@ -33,7 +33,7 @@ def new_generation(cells: List[List[int]], rule: List[int], time: int) -> List[i
     for i in range(population):
         # Get the neighbors of each cell
         left_neighbor = 0 if i == 0 else cells[time][i - 1]  # special: leftmost cell
-        right_neighbor = 0 if i == population - 1 else cells[time][i + 1]  # rightmost 
+        right_neighbor = 0 if i == population - 1 else cells[time][i + 1]  # rightmost
         # Define a new cell and add it to the new generation
         situation = 7 - int(f"{left_neighbor}{cells[time][i]}{right_neighbor}", 2)
         next_generation.append(rule[situation])