It's a way sellers describe serial numbers to make it sound like it is special when it is not. Would you pay more if oct-nary? That means each number is special because they don't repeat.
Agreed with the rest of you. It's not a repeated or any kind of fancy serial number...except maybe on eBay.
It is an ebay term. yes and an oct-nary, as you put it, some collectors collect them too. A note that doesn't have any repeat numbers sell on ebay all them time. I found out that there is a collector for all most any kind of serial number.