The package is here: Recamans.jl
Recamán’s sequence a_0, a_1, a_2\ldots is defined as:
a_n = \begin{cases}
0 && \text{if } n = 0 \\
a_{n - 1} -n && \text{if } a_{n - 1} -n > 0 \text{ and is not already in the sequence} \\
a_{n - 1} + n && \text{otherwise}
\end{cases}
This is not registered, and I have no plans to register it. I’m not opposed to it being added to another repo, say, of sequences, but I have no plans do so myself.