diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..7806da8
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+*.hi
+*.o
+*.prof
diff --git a/014-scanned.hs b/014-scanned.hs
new file mode 100644
index 0000000..401090d
--- /dev/null
+++ b/014-scanned.hs
@@ -0,0 +1,41 @@
+import Data.List
+type YInt = Int
+
+collatz :: YInt -> YInt
+collatz n
+    | n < 0 = 1
+    | even n = n `quot` 2
+    | otherwise = 3 * n + 1
+
+-- The l `seq` is necessary to not be lazy (non-strict)
+-- And not to fill the stack
+lencollatz' :: YInt -> YInt -> YInt
+lencollatz' l 1 = l
+lencollatz' l n = l `seq` lencollatz' (l + 1) (collatz n)
+
+lencollatz = lencollatz' 0
+
+-- The j `seq` is necessary to not be lazy (non-strict)
+-- And not to fill the stack
+maximalIndex :: (YInt, YInt) -> YInt -> [YInt] -> (YInt, YInt)
+maximalIndex (m, i) j [] = (m, i)
+maximalIndex (m, i) j (x : xs) = j `seq` maximalIndex res (j + 1) xs
+                              where res = if x > m then (x, j) else (m, i)
+
+showCollatz :: YInt -> String
+showCollatz 1 = "1"
+showCollatz n = show n ++ " → " ++ showCollatz ( collatz n )
+
+pure (Just x) = x
+
+main = do
+            putStrLn $ "max len: " ++ show m
+            putStrLn $ "max value: " ++ show i
+            -- print mrec
+            -- print irec
+            -- putStrLn $ showCollatz $ toInteger i
+       where
+            array = map lencollatz [1 .. 1000000]
+            m = maximum array
+            i = 1 + pure (elemIndex m array)
+            (mrec, irec) = maximalIndex (0, 0) 1 array
diff --git a/058.rb b/058.rb
index 1300186..a689a5b 100644
--- a/058.rb
+++ b/058.rb
@@ -1,3 +1,5 @@
+#!/usr/bin/env ruby
+# -*- encoding: utf-8 -*-
 problem=%{
 -- Starting with 1 and spiralling anticlockwise in the following way, a square spiral with side length 7 is formed.
 --
diff --git a/060 b/060
deleted file mode 100755
index 02eb239..0000000
Binary files a/060 and /dev/null differ
diff --git a/060-cheat.hs b/060-cheat.hs
new file mode 100644
index 0000000..f8b2d3f
--- /dev/null
+++ b/060-cheat.hs
@@ -0,0 +1,44 @@
+-- Problem 60
+-- 02 January 2004
+--
+-- The primes 3, 7, 109, and 673, are quite remarkable. By taking any two primes and concatenating them in any order the result will always be prime. For example, taking 7 and 109, both 7109 and 1097 are prime. The sum of these four primes, 792, represents the lowest sum for a set of four primes with this property.
+--
+-- Find the lowest sum for a set of five primes for which any two primes concatenate to produce another prime.
+--
+
+import Prime
+
+
+numOfDigits x
+    | x < 10 = 1
+    | x < 100 = 2
+    | x < 1000 = 3
+    | x < 10000 = 4
+    | x < 100000 = 5
+    | x < 1000000 = 6
+    | x < 10000000 = 7
+--    | otherwise = truncate (logBase 10 x)
+
+-- equivalent but faster than "read (show x ++ show y)"
+concatNumbers :: Int -> Int -> Int
+concatNumbers x y = (10^numOfDigits y)*x + y
+
+solve = do
+    a <- primesTo10000
+    let m = f a $ dropWhile (<= a) primesTo10000
+    b <- m
+    let n = f b $ dropWhile (<= b) m
+    c <- n
+    let o = f c $ dropWhile (<= c) n
+    d <- o
+    let p = f d $ dropWhile (<= d) o
+    e <- p
+    return [a,b,c,d,e]
+    where
+        f x = filter (\y -> all is_prime  [concatNumbers x y, concatNumbers y x])
+        primesTo10000 = takeWhile (<= 10000) primes
+
+
+main = do
+    print $ head $ solve
+    print $ sum $ head $ solve
diff --git a/060.hi b/060.hi
deleted file mode 100644
index 2226923..0000000
Binary files a/060.hi and /dev/null differ
diff --git a/060.hs b/060.hs
index 7a7c252..40f8434 100644
--- a/060.hs
+++ b/060.hs
@@ -1,50 +1,70 @@
--- 
--- The primes 3, 7, 109, and 673, are quite remarkable. 
--- By taking any two primes and concatenating them in any order the result will always be prime. 
--- For example, taking 7 and 109, both 7109 and 1097 are prime. 
--- The sum of these four primes, 792, represents the lowest sum for a set of four primes with this property.
+-- Problem 60
+-- 02 January 2004
+--
+-- The primes 3, 7, 109, and 673, are quite remarkable. By taking any two primes and concatenating them in any order the result will always be prime. For example, taking 7 and 109, both 7109 and 1097 are prime. The sum of these four primes, 792, represents the lowest sum for a set of four primes with this property.
 --
 -- Find the lowest sum for a set of five primes for which any two primes concatenate to produce another prime.
 --
 
--- Should use the following property
--- [x,y,z,t] special <=> [x,y,z] & [x,y,t] & [x,z,t] & [y,z,t] special
-
-
-import Debug.Trace
-import Data.List
 import Prime
 
-is_couple_prime x y = ( is_prime $ read $ strx ++ stry ) &&  (is_prime $ read $ stry ++ strx)
-    where
-        strx = show x
-        stry = show y
+numOfDigits x
+    | x < 10 = 1
+    | x < 100 = 2
+    | x < 1000 = 3
+    | x < 10000 = 4
+    | x < 100000 = 5
+    | x < 1000000 = 6
+    | x < 10000000 = 7
+--    | otherwise = truncate (logBase 10 x)
 
-first_concat_prime_with_list x [] = True
-first_concat_prime_with_list x (y:ys) = is_couple_prime x y && first_concat_prime_with_list x ys
+-- equivalent but faster than "read (show x ++ show y)"
+concatNumbers :: Int -> Int -> Int
+concatNumbers x y = (10^numOfDigits y)*x + y
 
--- are_concat_primes [3,7,109,673] return true if number are primes
--- even with concat
-are_concat_primes [] = True
-are_concat_primes (x:xs) = (are_concat_primes xs) && first_concat_prime_with_list x xs
+areConcatPrime :: [Int] -> Bool
+areConcatPrime [] = True
+areConcatPrime (x:xs) =
+    -- (areConcatPrime xs) && (and $ map concatPrime_x xs)
+    all concatPrime_x xs
+    where 
+        concatPrime_x :: Int -> Bool
+        concatPrime_x y = all is_prime [concatNumbers x y, concatNumbers y x]
 
-special_numbers 1 = take 300 primes
--- special_numbers n = nub $ flatten $ filter (\x -> traceShow x are_concat_primes x) $ subsets n (special_numbers (n-1))
-special_numbers n = nub $ flatten $ filter are_concat_primes $ subsets n (special_numbers (n-1))
-    where
-        flatten [] = []
-        flatten ([]:ys) = flatten ys
-        flatten ((x:xs):ys) = x:flatten (xs:ys)
 
-subsets :: Integer -> [a] -> [[a]]
-subsets 0 _ = [[]]
-subsets n [] = []
-subsets n (x:xs) = [x:ys | ys <- subsets (n-1) xs ] ++ subsets n xs
+-- for 1 should return a list of one element list containing a unique prime
+--
+cprimes :: Int -> [[Int]]
+cprimes n = concatMap (memoizedConcatPrimes n) [(n-1)..]
+
+-- concatPrimes' :: Int -> Int -> [[Int]]
+-- concatPrimes' 0 _ = [[]]
+-- concatPrimes' _ (-1) = error "concatPrimes' ERROR"
+-- concatPrimes' _ 0 = []
+-- concatPrimes' 1 max = [[ primes !! fromInt max ]]
+-- concatPrimes' n max = filter areConcatPrime [ p:cprimes | cprimes <- subsets  ]
+--     where p = primes !! fromInt max
+--           -- subsets = memoized !! fromInt (n-1)
+--           subsets = concatMap (concatPrimes' (n-1)) [0..(max-1)]
+
+memoizedConcatPrimes n max =
+    let p =  primes !! max
+        subsets = concatMap (memoizedConcatPrimes (n-1)) [0..(max-1)]
+        concatPrimes 0 _ = [[]]
+        concatPrimes _ 0 = []
+        concatPrimes 1 max = [[ primes !! max ]]
+        concatPrimes n max = filter areConcatPrime [p:cprimes | cprimes <- subsets ]
+    in  map (map concatPrimes [0..] !! n) [0..] !! max
 
 main = do
-        putStrLn $ show $ are_concat_primes [3,7,109,673]
-        putStrLn $ show $ numbers
-        putStrLn $ show $ result
-        where
-            numbers = take 5 $ special_numbers 5
-            result  = sum numbers
+    print $ take 20 $ cprimes 2
+    print $ cprimes 3 !! 0
+    print $ cprimes 3 !! 1
+    print $ cprimes 3 !! 2
+    print $ take 20 $ cprimes 3
+    print $ cprimes 4 !! 0
+    print $ cprimes 4 !! 1
+    print $ cprimes 4 !! 2
+    let res = take 3 $ cprimes 5
+    print res
+    print (map sum res)
diff --git a/060.o b/060.o
deleted file mode 100644
index b7926fd..0000000
Binary files a/060.o and /dev/null differ
diff --git a/060.rb b/060.rb
new file mode 100644
index 0000000..df3cb93
--- /dev/null
+++ b/060.rb
@@ -0,0 +1,32 @@
+#!/usr/bin/env ruby
+# -*- encoding: utf-8 -*-
+require './primes'
+$po = Primes.new(100)
+
+def concat_prime_with_set(n,set)
+    set.each do |m|
+        $po.is_prime( %{#{n}#{m}} ) and
+            $po.is_prime( %{#{m}#{n}} )
+    end
+end
+
+sets=Array.new
+
+sets[0]=Array.new
+$po.primes.each do |p|
+    break if p>1500
+    sets[0].append( [p] )
+end
+
+def create_set(n)
+    sets[n]=Array.new
+    $po.primes.each do |p|
+        break if p>1500
+        first_set.each do |qs|
+            sets[n].append( qs.append(p) ) if concat_prime_with_set p qs
+        end
+    end
+end
+
+create_set(1)
+print sets[1][0]
diff --git a/Prime.hi b/Prime.hi
deleted file mode 100644
index 558ddbb..0000000
Binary files a/Prime.hi and /dev/null differ
diff --git a/Prime.hs b/Prime.hs
index 77b9c0a..bf06453 100644
--- a/Prime.hs
+++ b/Prime.hs
@@ -3,7 +3,7 @@ module Prime
 , is_prime
 )
 where 
-    data Wheel = Wheel Integer [Integer]
+    data Wheel = Wheel Int [Int]
     roll (Wheel n rs) =  [n*k+r| k<-[0..], r<-rs]
     
     nextSize (Wheel n rs) p =
@@ -13,7 +13,7 @@ where
     
     mkWheel ds = foldl nextSize w0 ds
     
-    primes :: [Integer]
+    primes :: [Int]
     primes = small ++ large
         where
             1:p:candidates  = roll $ mkWheel small
diff --git a/Prime.o b/Prime.o
deleted file mode 100644
index d312344..0000000
Binary files a/Prime.o and /dev/null differ