Data update

Task/Duffinian-numbers/Lua/duffinian-numbers.lua

@@ -0,0 +1,58 @@
+function gcd(a, b)
+    while b ~= 0 do
+        a, b = b, a % b
+    end
+    return a
+end
+
+function duffinian(n)
+    if n == 2 then return false end
+    local total = 1
+    local power = 2
+    local m = n
+    while (n & 1) == 0 do
+        total = total + power
+        power = power << 1
+        n = n >> 1
+    end
+    local p = 3
+    while p * p <= n do
+        local sum = 1
+        local power = p
+        while n % p == 0 do
+            sum = sum + power
+            power = power * p
+            n = n / p
+        end
+        total = total * sum
+        p = p + 2
+    end
+    if m == n then return false end
+    if n > 1 then total = total * (n + 1) end
+    return gcd(total, m) == 1
+end
+
+print("First 50 Duffinian numbers:")
+count = 0
+n = 1
+while count < 50 do
+    if duffinian(n) then
+        count = count + 1
+        if count % 10 == 0 then space = 10 else space = 32 end
+        io.write(string.format('%3d%c', n, space))
+    end
+    n = n + 1
+end
+
+print("\nFirst 30 Duffinian triplets:")
+n = 1
+m = 0
+count = 0
+while count < 30 do
+    if duffinian(n) then m = m + 1 else m = 0 end
+    if m == 3 then
+        count = count + 1
+        print(string.format('%d, %d, %d', n - 2, n - 1, n))
+    end
+    n = n + 1
+end