I have been simulating artificial DNA sequences to try to understand how certain sequence characteristics influence the mutual information computed between two positions in a sequence across a large sample of sequences. The mutual information is essentially like a correlation that is appropriate for symbolic sequences rather than numeric values. One type of simulated sequence requires embedding short subsequences like NXYNZWNJK where N is always the same nucleotide but X,Y,Z,W,J,K are free to vary across instances of this short sequence. Another way to describe this is to say that the initial nucleotide repeats at multiples of distance 3 bp: positions 1, 4, 7, 10, etc. This is different from a true trinucleotide repeat such as NXYNXYNXY in which the whole trinucleotide repeats a variable number of times.
My question is this: Is there a formal name for this kind of repeat structure? As I said above, I can't refer to it as a true trinucleotide repeat, but I am wondering if this kind of repeating nucleotide with interleaved nucleotides that are free to vary has a formal name in the literature. I have been referring to them in the paper that I am writing as "hollow" trinucleotide repeats in the sense that the structure of a true trinucleotide repeat has been "hollowed" out leaving only the initial nucleotide repeating with the other positions basically serving as placeholders, but I don't want to invent a new term if there is already a formal way of referring to this kind of repeat. This is especially true if I am overlooking some aspect of this sequence characteristic that goes by a different name.
Any help would be appreciated.