1 files changed, 31 insertions, 0 deletions
diff --git a/12.lua b/12.lua
new file mode 100644
index 0000000..7ef1c0d
--- /dev/null
+++ b/12.lua
@@ -0,0 +1,31 @@
+-- only valid when n > 1
+function num_factors(n)
+    local ret = 2
+    local test = 2
+    local limit = math.sqrt(n)
+    while test < limit do
+        if n % test == 0 then
+            ret = ret + 2
+        end
+        test = test + 1
+    end
+    if limit == math.floor(limit) then ret = ret + 1 end
+    return ret
+end
+
+generate_triangle = coroutine.wrap(function()
+    local num = 0
+    local add = 1
+    while true do
+        num = num + add
+        add = add + 1
+        coroutine.yield(num)
+    end
+end)
+
+while true do
+    local n = generate_triangle()
+    local nn = num_factors(n)
+    print(n .. ": " .. nn)
+    if nn > 500 then break end
+end