Weird backlink anchor pattern

It's been a while now that I find a strange anchor pattern which looks like this:
, 81 , o , b, r , a ,
(backlink)
, g , j , 0n, 5 , f2 ,
(backlink)
, b , j , p, f , bh ,
(backlink)
, rl , b , t, x , h ,
(backlink)
..and so on.

That kind of pattern has appeared so far on dozens -if not hundreds- of domains and it floods all backlinks of a domain.

Anyone knows what possible benefit can that pattern have?
I mean, why not insert a random word or just gibberish, why follow that particular pattern?

thanks

 

No SEO guys on the forum?

Any opinion is welcome, even if you are not absolutely sure.