<html><head/><body><html><head></head><body>For one thing, the question you are asking in the code, (> i 4) ;; i.e., i > 4 is not the same question you ask in your equations, n < 4 so, for starters, it would seem you need the two questions to be in agreement. Best, jmj -- Sent from my Android phone with K-9 Mail. <div class="gmail_quote">Robert Hume <rhume55@gmail.com> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> I'm really stuck trying to figure this out. Any pointers are useful! Here's the problem: f(n) = n if n<4 and f(n) = f(n - 1) + 2f(n - 2) + 3f(n - 3) + 4f(n - 4) if n>= 4 Here's my solution so far -- any one know what I'm doing wrong? (define (f n) (define (f-iter result i) (if (> i 4) result (f-iter (+ result (* i (- n i))) (+ i 1)) ) ) (if (< n 4) n (f-iter 0 1) ) ) (f 4) ;; should produce 10, produces 10 (f 5) ;; should produce 26, produces 20 (f 6) ;; should produce 63, produces 30 <pre style="white-space: pre-wrap; word-wrap:break-word; font-family: monospace; margin-top: 0px">____________________ Racket Users list: <a href="http://lists.racket-lang.org/users">http://lists.racket-lang.org/users</a> </pre></blockquote></div></body></html></body></html>