User blog:Vel!/Factoid notation

Yet another factorial array notation. It doesn't quite work yet.

\[!\langle n \rangle = n\]

\[!\langle 1, # \rangle = 1\]

\[!\langle n, a, \# \rangle = \prod_{k = 1}^{n} !\langle k, a - 1, \# \rangle\]

\[!\langle n, 1, \ldots, 1, 1, a, \# \rangle = !\langle n, n, \ldots, !\langle n - 1, 1, \ldots, 1, 1, a - 1, \# \rangle, a - 1, \# \rangle\]

\[!\langle \#, 1 \rangle = !\langle \# \rangle\]