sum(2^k, k=1, n)
Let's evaluate: k = 1n2k
For K = abc(K + d), the following formula applies: c(a + d)·c(b -a + 1) -1c -1
2·2(n -1 + 1) -12 -1
2·2(n -1 + 1) -12 -1 = 2·(2(n -1 + 1) -1)2 -1-1 + 1 = 02 -1 = 1
2·(2(n + 0) -1)1
Result:   2·(2n -1)