First version of the function

nbackseq

@@ -1,10 +1,33 @@
 #!/usr/bin/env python
+
+import random
 import sys
 
 
 def nbackseq(n, length, words):
-    pass
+    seq = []
+    if length > n:
+        # first make a list with length of n
+        seq.extend(random.sample(words, n))
+        # now add entries one by one
+        for i in range(n, length):
+            seq.extend(random.sample(words, 1))
+            # check if entry is not repeated in the previous n entries
+            while len(seq[-n:]) != len(set(seq[-n:])):
+                seq.pop()
+                seq.extend(random.sample(words, 1))
+    # pick length items
+    elif length <= n:
+        unique_words = random.sample(words, length)
+        seq.extend(unique_words)
+    return seq
 
 
 if __name__ == '__main__':
-    print(sys.argv)
+    n = int(sys.argv[1])
+    length = int(sys.argv[2])
+    words = sys.argv[3:]
+    if len(words) != len(set(words)):
+        raise ValueError('Your input words are not unique!')
+    seq = nbackseq(n, length, words)
+    print(seq)