Induktionsanfang n = 1 ; n = 2
f1 = (2^{1 - 1} + (-1)^1)/3 = 0
f2 = (2^{2 - 1} + (-1)^2)/3 = 1
Induktionsschritt: n --> n+1
fn+1 = fn + 2fn-1
(2^ ((n + 1) - 1) + (-1)^{n + 1})/3 = (2^{n - 1} + (-1)^n)/3 + 2·(2^ ((n - 1) - 1) + (-1)^{n - 1})/3
2^n - (-1)^n = 1/2·2^n + (-1)^n + 2·(1/4·2^n - (-1)^n)
2^n - (-1)^n = 1/2·2^n + (-1)^n + 1/2·2^n - 2·(-1)^n
2^n - (-1)^n = 2^n - (-1)^n
wzbw.