Even / odd binomial sums (For n≥1, sums of even-r and odd-r binomial coeffs each equal 2^{n−1}.)

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For n≥1, sums of even-r and odd-r binomial coeffs each equal 2^{n−1}.

What each symbol means

SymbolWhat it stands for
nPositive integer

When to use this

From (1+1)^n and (1−1)^n.