CombinatorialHierarchy.hs

module CombinatorialHierarchy where

{- https://en.wikipedia.org/wiki/Combinatorial_hierarchy

3, 2^3-1, 2^7-1, 2^127-1

seq:
    3, 7,     127,   170141183460469231731687303715884105727

cumulative sum:
    3, 10,    137,   170141183460469231731687303715884105864
-}

combinatorialHierarchy = cumSum (take 4 (conseq 3))
  where conseq :: Integer -> [Integer]
        conseq n = n : conseq (nxt n)
        nxt n    = 2^n - 1
        cumSum   = scanl1 (+)

main = print combinatorialHierarchy

{-
$ ghci CombinatorialHierarchy.hs
...
> main
[3,10,137,170141183460469231731687303715884105864]
> 
-}