Recursionhard
0:00.0

A recurrence is defined as an=an1+2an2a_n = a_{n-1} + 2a_{n-2} for n2n \geq 2, with a0=1a_0 = 1 and a1=1a_1 = 1. Let A(x)=n=0anxnA(x) = \sum_{n=0}^{\infty} a_n x^n be the ordinary generating function. Which of the following is the correct rational form of A(x)A(x)?