diff --git a/diversity.cabal b/diversity.cabal
--- a/diversity.cabal
+++ b/diversity.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                diversity
-version:             0.3.4.0
+version:             0.3.4.1
 synopsis:            Return the diversity at each position for all sequences in a fasta file
 description:         Find the diversity of a collection of entities, mainly for use with fasta sequences. Produces a binary which works on fasta files to find the diversity of any order and rarefaction curves for a sliding window across all positions in the sequences. To analyze just a collection of entities, just use the whole sequences and list flag.
 homepage:            https://github.com/GregorySchwartz/diversity
diff --git a/src/src-exec/Main.hs b/src/src-exec/Main.hs
--- a/src/src-exec/Main.hs
+++ b/src/src-exec/Main.hs
@@ -76,7 +76,8 @@
          <> value "1 1"
          <> help "The start point and interval of subsamples in the\
                  \ rarefaction curve. For instance, '1 1' would be 1, 2, 3, ...\
-                 \ '2 6' would be 2, 8, 14, ..." )
+                 \ '2 6' would be 2, 8, 14, ... Note: input is a string so\
+                 \ use quotations around the entry" )
       <*> switch
           ( long "fast-bin"
          <> short 'f'
diff --git a/src/src-lib/Math/Diversity/Diversity.hs b/src/src-lib/Math/Diversity/Diversity.hs
--- a/src/src-lib/Math/Diversity/Diversity.hs
+++ b/src/src-lib/Math/Diversity/Diversity.hs
@@ -16,7 +16,6 @@
 import Data.List
 import Data.Ratio
 import qualified Data.Set as Set
-import qualified Data.Foldable as F
 import Numeric.SpecFunctions (choose)
 import Data.Function (on)
 
@@ -77,7 +76,6 @@
 getSampleContents = map (Set.fromList . map snd)
                   . groupBy ((==) `on` fst)
                   . sortBy (compare `on` fst)
-                  . map (\(!x, !y) -> (x, y))
 
 -- | Returns the rarefaction curve for each position in a list
 rarefactionSampleCurve :: (Ord a, Ord b)
@@ -93,21 +91,21 @@
         | t == 0       = (t, 0)
         | t == t_total = (t, richness)
         | otherwise    = (t, richness - inner t)
-    inner t = ( \x -> if fastBin
-                        then x / choose t_total t
-                        else x )
-            . F.sum
-            . Set.map ( \s -> specialBinomial
+    inner t     = ( \x -> if fastBin
+                            then x / choose t_total t
+                            else x )
+                . sum
+                . map ( \s -> specialBinomial
                               fastBin
                               (fromIntegral t_total)
                               (numHave s samples)
                               (fromIntegral t) )
-            $ speciesList
-    numHave s = sum . map (\x -> if Set.member s x then 1 else 0)
-    richness = fromIntegral . Set.size $ speciesList
-    speciesList = Set.fromList . map snd $ ls
-    t_total = genericLength samples
-    samples = getSampleContents ls
+                $ speciesList
+    numHave s   = sum . map (\x -> if Set.member s x then 1 else 0)
+    richness    = genericLength speciesList
+    speciesList = nub . map snd $ ls
+    t_total     = genericLength samples
+    samples     = getSampleContents ls
 
 -- | Calculates the percent of the curve that is above 95% of height of the curve
 rarefactionViable :: [Double] -> Double