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  1. import itertools
  2.  
  3. m = 2
  4.  
  5. def has(x):
  6.   for i in x:
  7.     for j in x:
  8.       if i + j == 0:
  9.         return True
  10.   return False
  11.  
  12. def rec(n,k):
  13.   if n == 0: 
  14.     return 1
  15.   return (2 * m - 2 * k) * rec(n - 1, k + 1) + k * rec(n - 1, k)
  16.  
  17. for n in xrange(1, 10):
  18.   c = 0
  19.   for i in itertools.product([i for i in xrange(-m, 1 + m) if i], repeat=n):
  20.     if not has(i):
  21.       c += 1
  22.   print "brute force: ",n, c
  23.   print "recurrence:" ,n, rec(n,0)
  24.  
  25.  
Success #stdin #stdout 0.38s 7852KB
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brute force:  1 4
recurrence: 1 4
brute force:  2 12
recurrence: 2 12
brute force:  3 28
recurrence: 3 28
brute force:  4 60
recurrence: 4 60
brute force:  5 124
recurrence: 5 124
brute force:  6 252
recurrence: 6 252
brute force:  7 508
recurrence: 7 508
brute force:  8 1020
recurrence: 8 1020
brute force:  9 2044
recurrence: 9 2044
https://ideone.com/00DlhL
language:
Python (cpython 2.7.16)
created:
12 years ago
visibility:
public

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