From 7a504ce6afeb14aa86c830260f0693262a20f9df Mon Sep 17 00:00:00 2001
From: Roger Bell_West <roger@firedrake.org>
Date: Mon, 6 Jun 2022 09:36:01 +0100
Subject: Solutions for challenge #168

---
 challenge-168/roger-bell-west/python/ch-1.py | 52 ++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100755 challenge-168/roger-bell-west/python/ch-1.py

(limited to 'challenge-168/roger-bell-west/python/ch-1.py')

diff --git a/challenge-168/roger-bell-west/python/ch-1.py b/challenge-168/roger-bell-west/python/ch-1.py
new file mode 100755
index 0000000000..70bf8b3303
--- /dev/null
+++ b/challenge-168/roger-bell-west/python/ch-1.py
@@ -0,0 +1,52 @@
+#! /usr/bin/python3
+
+import unittest
+
+from math import sqrt,floor,log
+from collections import deque
+
+def isprime(candidate):
+  if candidate < 2:
+    return False
+  elif candidate==2:
+    return True
+  elif candidate==3:
+    return True
+  elif candidate % 2 == 0:
+    return False
+  elif candidate % 3 == 0:
+    return False
+  anchor = 0
+  limit = int(sqrt(candidate))
+  while True:
+    anchor += 6
+    for t in range(anchor-1,anchor+2,2):
+      if t > limit:
+        return True
+      if candidate % t == 0:
+        return False
+
+def perrinprime(n):
+  out = set()
+  seq = deque([3, 0, 2])
+  while True:
+    nv = seq[0] + seq[1]
+    seq.popleft()
+    seq.append(nv)
+    if isprime(nv):
+      out.add(nv)
+      if len(out) >= n:
+        break
+  o = list(out)
+  o.sort()
+  return o
+
+class TestPerrinprime(unittest.TestCase):
+
+        def test_ex1(self):
+          self.assertEqual(perrinprime(13),
+                           [2, 3, 5, 7, 17, 29, 277, 367, 853, 14197,
+                            43721, 1442968193,
+                            792606555396977],'example 1')
+
+unittest.main()
-- 
cgit