From Stephen Sheen
Every time someone writes about the number of permutations of 52 playing cards they seem to set down a different answer. Erica Klarreich says it is roughly 1058 in your feature (20 July, p 42). Surely it is closer to 1068 or 8 × 1067 – 52 factorial?
Perhaps the true number is actually a “recipriversexclusion” – a number whose existence can only be defined as being anything other than itself, a concept proposed by Douglas Adams in Life, the Universe and Everything.
This is correct. It means that the comparison with atoms in the Sun is less apt than it might be. It is more like the atoms in the Galaxy – Ed.
Gooseberry Hill, West Australia
