diff --git a/level5/expanding-nebula/solution.py b/level5/expanding-nebula/solution.py
index b70b650..deda8db 100644
--- a/level5/expanding-nebula/solution.py
+++ b/level5/expanding-nebula/solution.py
@@ -8,25 +8,26 @@ def solution(g):
     #print height, width
 
     memo = {}
-    prev_cases = {}
-    for i in range(2**(height+1)):
-        prev_cases[i] = 1
-        memo[i] = {}
-        for j in range(2**(height+1)):
-            memo[i][j] = calculate_c_column(i, j, height)
+    prev_cases = {i:1 for i in range(2**(height+1))}
+    #for i in range(2**(height+1)):
+    #    prev_cases[i] = 1
+    #    memo[i] = {j:calculate_c_column(i, j, height) for j in range(2**(height+1))}
     #print memo
 
     #print prev_cases
     for column in range(width):
         cases = {}
-        for i in range(2**(height+1)):
-            cases[i] = 0
+        c = list_to_int(grid[:,column])
         #print grid[:,column], list_to_int(grid[:,column])
-        for i in range(2**(height+1)):
-            if prev_cases[i] == 0:
-                continue
-            for j in range(2**(height+1)):
-                if memo[i][j] == list_to_int(grid[:,column]):
+        for i in prev_cases.keys():
+            if not i in memo:
+                memo[i] = {}
+            if not c in memo[i]:
+                memo[i][c] = [j for j in range(2**(height+1)) if calculate_c_column(i, j, height) == c]
+            for j in memo[i][c]:
+                if not j in cases:
+                    cases[j] = 0
+                if i in prev_cases:
                     cases[j] += prev_cases[i]
         #print cases
         prev_cases = cases
@@ -43,11 +44,11 @@ def print_grid(g):
         print line
 
 def calculate_c_column(i, j, length):
-    mask = 2**(length)-1
-    multi_ones = ((i&j)|((i&j)>>1)) & mask
+    mask = 2**length-1
+    multiple_ones = ((i&j)|((i&j)>>1)) & mask
     odd_ones = ((i^j)^((i^j)>>1)) & mask
-    single_one = (~multi_ones & odd_ones) & mask
-    #print ' '.join(('{:0'+str(length)+'b}').format(k) for k in [i, j]), ' '.join(('{:0'+str(length-1)+'b}').format(k) for k in [multi_ones, odd_ones, single_one])
+    single_one = (~multiple_ones & odd_ones) & mask
+    #print ' '.join(('{:0'+str(length)+'b}').format(k) for k in [i, j]), ' '.join(('{:0'+str(length-1)+'b}').format(k) for k in [multiple_ones, odd_ones, single_one])
     return single_one
 
 #l=3
@@ -78,6 +79,7 @@ tests = [
             ([[True, False]], 10),
             ([[False, True]], 10),
             ([[False, False]], 38),
+            #([[True, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], [False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], [False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], [False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], [False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], [False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], [False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], [False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False], [False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False]], 1),
         ]
 
 for (i, o) in tests: