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Climbing ten steps using only odd-sized jumps

Question

A rabbit at the bottom of a 1010-step staircase climbs to the top using jumps that each cover an odd number of steps (11, 33, 55, …). How many different jump sequences take it exactly to the top of the tenth step?

Short answer

5555. Let ono_n count ways to climb nn steps. Splitting on whether the first jump is 11 or larger (a jump of j≥3j\ge3 is like a jump of j−2j-2 from two steps higher) gives on=on−1+on−2o_n=o_{n-1}+o_{n-2} with o1=o2=1o_1=o_2=1, so ono_n is Fibonacci and o10=55o_{10}=55.

Adapted from QuantQuestions.io; question and answer rewritten by SelfMadeQuant.com.

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