diff --git a/mad/fib.mad b/mad/fib.mad
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--- /dev/null
+++ b/mad/fib.mad
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+; Functions to calculate Fibonacci numbers
+
+; Slow recursive version
+(def slowFib (fn (n) (if (< n 2) n (+ (slowFib (- n 1)) (slowFib (- n 2))))))
+
+; Return the sum of the last 2 numbers in a sequence
+(def sumOfLast (fn (l) (+ (last l) (get l (- (len l) 2)))))
+
+; Faster version, return vector of n numbers
+(def fibListRec (fn (n l) (if (< (len l) n) (fibListRec n (push l (sumOfLast l))) l)))
+(def fibList (fn (n) (fibListRec n [0 1])))