Nested Cascading Hyper Notation (NCHN) is the 10th part of HN.
An expression is of the form H_m<n,A>, where n is the base, m is the secondary base, and A is an array.
As always, this part uses the same definitions as ACHN.
As you can see, the rules have been edited. This is, so we can apply HN expressions to X. So N{x}M is now H_N<M,x>. However, we need to replace N and M into (N) and (M), because else some expressions will have multiple definitions and infinite loops. However, (N) and (M) are still arrays, but any (N)# and (M)# is lower than (1,2)# (where # is rest of array).
So, two more things. If, when solving H_m<n,A>, you find an (N):
If the N is sequence array, ignore N, except for the leftmost entry, then solve like normal.
If the N is limit array, the xth member of (N)'s FS is (FS(N,x)).
Also, (x) = x.
And, to compare arrays, just compare the HN expressions or use ACHN rules.