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If $$26\left(\frac{2^3}{3} {^{12} C_{2}} + \frac{2^5}{5} {^{12} C_{4}} + \frac{2^7}{7} {^{12} C_{6}} + \cdots + \frac{2^{13}}{13} {^{12} C_{12}}\right) = 3^{13} - \alpha$$, then $$\alpha$$ is equal to :
$$\frac{1}{k} \, ^nC_{k-1} = \frac{1}{n+1} \, ^{n+1}C_k$$
$$(1+x)^m = \sum_{k=0}^{m} \, ^mC_k x^k$$
$$S = \sum_{k=1}^{6} \frac{2^{2k+1}}{2k+1} \, ^{12}C_{2k}$$
$$S = \frac{1}{13} \sum_{k=1}^{6} 2^{2k+1} \, ^{13}C_{2k+1}$$ ($$\frac{1}{2k+1} \, ^{12}C_{2k} = \frac{1}{13} \, ^{13}C_{2k+1}$$)
$$S = \frac{2}{13} \sum_{k=1}^{6} 2^{2k} \, ^{13}C_{2k+1} = \frac{2}{13} \sum_{k=1}^{6} (2^2)^k \, ^{13}C_{2k+1}$$
$$S = \frac{2}{13} \sum_{k=1}^{6} 4^k \, ^{13}C_{2k+1}$$
Now, consider the expansion $$(1+x)^{13} = \, ^{13}C_0 + \, ^{13}C_1 x + \, ^{13}C_2 x^2 + \dots + \, ^{13}C_{13} x^{13}$$.
For $$x=2$$: $$(1+2)^{13} = 3^{13} = \sum_{r=0}^{13} \, ^{13}C_r 2^r$$
For $$x=-2$$: $$(1-2)^{13} = -1 = \sum_{r=0}^{13} \, ^{13}C_r (-2)^r$$
Subtracting the two:
$$3^{13} - (-1) = \sum_{r=0}^{13} \, ^{13}C_r (2^r - (-2)^r) = 2 \sum_{k=0}^{6} \, ^{13}C_{2k+1} 2^{2k+1}$$
$$3^{13} + 1 = 2 \left( \, ^{13}C_1 2^1 + \sum_{k=1}^{6} \, ^{13}C_{2k+1} 2^{2k+1} \right)$$
$$3^{13} + 1 = 2(13 \cdot 2 + 2 \sum_{k=1}^{6} \, ^{13}C_{2k+1} 4^k)$$
$$3^{13} + 1 = 52 + 4 \sum_{k=1}^{6} \, ^{13}C_{2k+1} 4^k$$
$$3^{13} - 51 = 4 \sum_{k=1}^{6} \, ^{13}C_{2k+1} 4^k$$
Since $$S = \frac{2}{13} \sum_{k=1}^{6} 4^k \, ^{13}C_{2k+1}$$, then $$13S = 2 \sum_{k=1}^{6} 4^k \, ^{13}C_{2k+1}$$:
$$26S = 4 \sum_{k=1}^{6} 4^k \, ^{13}C_{2k+1} = 3^{13} - 51$$
The original expression is $$26S = 3^{13} - \alpha$$. Comparing this to our derived $$26S = 3^{13} - 51$$, we find:
$$\alpha = 51$$
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