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TakashiHarada/number_of_rulelist_pattern.hs

Created March 14, 2018 03:37
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number_of_rulelist_pattern.hs
fact :: Integer -> Integer
fact n = product [1..n]
comb :: Integer -> Integer -> Integer
comb n k = product [(n-k+1)..n] `div` (fact k)
f :: Integer -> Integer
f w = sum [(comb (3^w) k) * (fact k) * 2^k | k <- [1..3^w]]
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