Euler problems/21 to 30
Evaluate the sum of all amicable pairs under 10000.
problem_21 = undefined
What is the total of all the name scores in the file of first names?
-- apply to a list of names problem_22 :: [String] -> Int problem_22 = sum . zipWith (*) [ 1 .. ] . map score where score = sum . map ( subtract 64 . ord )
Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers.
problem_23 = undefined
What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?
perms  = [] perms xs = do x <- xs map ( x: ) ( perms . delete x $ xs ) problem_24 = ( perms "0123456789" ) !! 999999
What is the first term in the Fibonacci sequence to contain 1000 digits?
valid ( i, n ) = length ( show n ) == 1000 problem_25 = fst . head . filter valid . zip [ 1 .. ] $ fibs where fibs = 1 : 1 : 2 : zipWith (+) fibs ( tail fibs )
Find the value of d < 1000 for which 1/d contains the longest recurring cycle.
problem_26 = undefined
Find a quadratic formula that produces the maximum number of primes for consecutive values of n.
problem_27 = undefined
What is the sum of both diagonals in a 1001 by 1001 spiral?
problem_28 = undefined
How many distinct terms are in the sequence generated by ab for 2 ≤ a ≤ 100 and 2 ≤ b ≤ 100?
problem_29 = undefined
Find the sum of all the numbers that can be written as the sum of fifth powers of their digits.
problem_30 = undefined