cute and reasonably fast lazy ramanujan numbers

ramanujan.hs

zipper xs = ([], xs)

next (xs, y:ys) = (y:xs, ys)
next z          = z

rmj n = take n naive
  where
    naive = go $ zipper [ x^3 + y^3 | x <- [1..], y <- [1..x] ]
    go    (_,[])  = []
    go xs@(l,n:_) = let ns = go $ next xs in
       if elem n l then n : ns else ns

main = print $ rmj 100