Create collatz_sequence.py

Author: SandersLin

collatz_sequence.py

@@ -0,0 +1,25 @@
+def collatz_sequence(n):
+  """Collatz conjecture: start with any positive integer n.Next termis obtained from the previous term as follows: 
+  if the previous term is even, the next term is one half the previous term. 
+  If the previous term is odd, the next term is 3 times the previous term plus 1. 
+  The conjecture states the sequence will always reach 1 regaardess of starting n."""
+  sequence = [n]
+  while n != 1:
+    if n % 2 == 0:# even
+      n //= 2 
+    else:
+      n = 3*n +1
+    sequence.append(n)
+  return sequence
+
+
+def main():
+  n = 43
+  sequence = collatz_sequence(n)
+  print(sequence)
+  print("collatz sequence from %d took %d steps."%(n,len(sequence)))
+
+
+
+if __name__ == '__main__':
+  main()