It’s a precalculus holiday equation. need to simplify to find the “secret message” can anyone

Take the expression in chunks:

>>

>>

>>

Note that . So

where the cyclic sum notation means

In other words, we take the sum over all possible cycles of the sequence of arguments to the summand. The second square-bracketed chunk reduces to

So to recap, we've reduced the starting expression to

>>

Finally, we have

Then distributing and rewriting to decode the message, we have

keene f. ffnfnfnfnfnfnfn f bfnfnfnfnfj