egison-3.3.7: lib/math/euler.egi

;;;;;
;;;;; Functions to solve Project Euler
;;;;;

(define $sum-of-positive-divisors
  (lambda [$n]
    (foldl' * 1 (map (lambda [$p $c] (/ (- (power p (+ c 1)) 1) (- p 1))) (frequency (p-f n))))))

(define $sum-of-proper-divisors
  (lambda [$n]
    (- (sum-of-positive-divisors n) n)))