From 89b75091efcc8ab7ec62564a9dbe319cb0552eba Mon Sep 17 00:00:00 2001
From: Roger Bell_West <Firedrake@users.noreply.github.com>
Date: Mon, 10 Jan 2022 10:58:14 +0000
Subject: Solutions for challenge #147

---
 challenge-147/roger-bell-west/lua/ch-2.lua | 41 ++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100755 challenge-147/roger-bell-west/lua/ch-2.lua

(limited to 'challenge-147/roger-bell-west/lua/ch-2.lua')

diff --git a/challenge-147/roger-bell-west/lua/ch-2.lua b/challenge-147/roger-bell-west/lua/ch-2.lua
new file mode 100755
index 0000000000..c46defd3d4
--- /dev/null
+++ b/challenge-147/roger-bell-west/lua/ch-2.lua
@@ -0,0 +1,41 @@
+#! /usr/bin/lua
+
+function pentagon(n)
+   return math.floor(n*(3*n-1)/2)
+end
+
+function pentpair()
+   fpent={}
+   rpent={}
+   mx=0
+   a=1
+   while 1 do
+      while mx < a do
+         mx = mx + 1
+         table.insert(fpent,pentagon(mx))
+         rpent[fpent[mx]]=mx
+      end
+      for b = 1,a do
+         d=fpent[a]-fpent[b]
+         if d < fpent[b] then
+            break
+         end
+         if rpent[d] ~= nil then
+            s=fpent[a]+fpent[b]
+            while s > fpent[mx] do
+               mx = mx + 1
+               table.insert(fpent,pentagon(mx))
+               rpent[fpent[mx]]=mx
+            end
+            if rpent[s] ~= nil then
+               print(string.format("P(%d) + P(%d) = %d + %d = %d = P(%d)",a,b,fpent[a],fpent[b],s,rpent[s]))
+               print(string.format("P(%d) - P(%d) = %d - %d = %d = P(%d)",a,b,fpent[a],fpent[b],d,rpent[d]))
+               os.exit(0)
+            end
+         end
+      end
+      a = a + 1
+   end
+end
+
+pentpair()
-- 
cgit