Amusements in Mathematics
In the making or solving of double acrostics, has it ever occurred to you to consider the
variety and limitation of the pair of initial and final letters available for cross words? You
may have to find a word beginning with A and ending with B, or A and C, or A and D,
and so on. Some combinations are obviously impossible—such, for example, as those
with Q at the end. But let us assume that a good English word can be found for every
case. Then how many possible pairs of letters are available?