[tex] {2}^{n + 1} + 3 \times 2 ^{n } + 2 ^{n + 3} \\ {2}^{n} \times {2}^{1} + 3 \times 2 ^{n } + 2 ^{n } \times {2}^{3} \\ {2}^{n} \times (2 + 3 + 8) = {2}^{n} \times13[/tex]
a)
1. n = 2
=> a = 2^2 * 13 = 4 * 13 = 52
2. n = 3
=> a = 2^3 * 13 = 8 * 13 = 104