7 lines
310 B
Haskell
7 lines
310 B
Haskell
-- How many n-digit positive integers exist which are also an nth power?
|
|
import Data.List (nub)
|
|
|
|
-- If x >= 10 then x^n >= 10^n and thus has more than n digits.
|
|
-- If n >= 22 then 9^n < 10^(n-1) and thus has fewer than n digits.
|
|
main = print $ length $ nub [ x^n | n <- [1..21], x <- [1..9], x^n >= 10^(n-1) ]
|