There are twenty-six letters in the alphabet, giving 325 different pairs. Every one of these pairs may be reversed, making 650 ways. But every initial letter may be repeated as the final, producing 26 other ways. The total is therefore 676 different pairs. In other words, the answer is the square of the number of letters in the alphabet.
287.--AN ACROSTIC PUZZLE.
From Amusements in Mathematics by Henry Ernest Dudeney.
