Word search puzzles have, like crosswords and arrowords, been very popular in the United Kingdom, and - also in common with these latter puzzles - have had complete magazines devoted to them. Word searches are commonly found in daily newspapers and puzzle books. Some teachers use them as educational tools for children, the benefit being that young minds can learn new words and their spellings by intensively searching for them, letter by letter, in the puzzle. A common strategy for finding all the words is to go through the puzzle left to right (or vice versa) and look for the first letter
Square-free word first difference of the Thue–Morse sequence. That is, from the Thue–Morse sequence one forms a new sequence in which each term is the difference of two consecutive terms of the Thue–Morse sequence. The resulting square-free word is Another example found by John Leech is defined recursively over the alphabet {"a, b, c"}. Let formula_1 be any word starting with the letter "a". Define the words formula_2 recursively as follows: the word formula_3 is obtained from formula_4 by replacing each "a" in formula_4 with , each "b" with , and each "c" with . It is possible to check that the