Auto-numbering in Increments of 5

After the idea from Bob my solution in FMcalc seems to be an overkill. With special markers any series can be built. Even random numbers are possible - fun for marketing people...

FM is pretty weak on extra syntax in expression constructs, and on arbitrary auto sequences (except in footnotes, oddly, but this can't be easily exploited for n+5).

I'd be tempted to implement it as a table on a Reference Page (or Pages, auto-connected as needed).
Col 1: n+ autonumber only

Col 2: full SKU, if any
Col 3: formal SKU description

Col 4,5,6,7: n+ {this consumes the next 4 ANs)

Each new row thus auto-starts as n+5 in its Col1
Doc body invokes these by Xref.
Rows in RP table can be re-organized as needed, and doc body updates automatically.