Extraction Problem of the Pell Sequence
Wai-Fong Chuan, Fei Richard Yu · The Fibonacci Quarterly · 2000
Let A be an alphabet and let A * be the free monoid over A. Let A + = A * \\{e}, where s denotes the empty word. For w e A*, let \\w \\ denote the length of w. Let \\s\\ = 0. A word x is said to be & prefix of a finite or infinite word w over A if x e A + and there is a word y such that w — xy. The finite or infinite word y is called a suffix of w. Let R be the reversion operator on