1.11.iter.scm

#lang scheme
(define (f n)
  (define (iter a b c count)
    (if (> count n)
        a
        (iter (+ a 
                 (* 2 b)
                 (* 3 c))
              a
              b
              (+ count 1))))
  (if (< n 3)
      n
      (iter 2 1 0 3)))