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+#!/usr/bin/env lua
+
+--[[
+Challenge 102
+
+TASK #2 > Hash-counting String
+Submitted by: Stuart Little
+
+You are given a positive integer $N.
+
+Write a script to produce Hash-counting string of that length.
+
+The definition of a hash-counting string is as follows:
+- the string consists only of digits 0-9 and hashes, '#'
+- there are no two consecutive hashes: '##' does not appear in your string
+- the last character is a hash
+- the number immediately preceding each hash (if it exists) is the position
+of that hash in the string, with the position being counted up from 1
+
+It can be shown that for every positive integer N there is exactly one such
+length-N string.
+Examples:
+
+(a) "#" is the counting string of length 1
+(b) "2#" is the counting string of length 2
+(c) "#3#" is the string of length 3
+(d) "#3#5#7#10#" is the string of length 10
+(e) "2#4#6#8#11#14#" is the string of length 14
+--]]
+
+function hash_counting(n)
+    local out, i = '', n
+    while i > 0 do
+        p = i
+        out = '#'..out
+        i = i - 1
+        while i > 0 and p ~= 0 do
+            out = tostring(p % 10)..out
+            i = i - 1
+            p = math.floor(p / 10)
+        end
+    end
+    return out
+end
+
+print(hash_counting(tonumber(arg[1])))