2017 UNM-PNM Statewide High School Mathematics Contest II Problems/Problem 7

Problem

Find a formula for $\sum_{k=0}^{\lfloor \frac{n}{4} \rfloor } \binom{n}{4k}$ for any natural number $n$ .

$\frac{2^n+(1+i)^n+(1-i)^n}{4}$

2017 UNM-PNM Contest II (Problems • Answer Key • Resources)
Preceded by Problem 6	Followed by Problem 8
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