I thougth a hash might be faster, but no. 

        Rate hash   if
hash  9329/s   -- -11%
if   10473/s  12%   --

        Rate hash   if
hash  9436/s   -- -11%
if   10599/s  12%   --

        Rate hash   if
hash  9341/s   -- -12%
if   10662/s  14%   --

[download]

Benchmark code:

<Reveal this spoiler or all in this thread>

A hash is definitely cleaner, though.

In reply to Re^2: Speeding permutation counting by ikegami
in thread Speeding permutation counting by albert

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