merge(concantenate) cells by order

In column A there are items like a,b,c,d,e,f,g,..... and goes on.
I want to merge(concantenate) items in column B like ab, ac,ad,ae,af,ag,bc,bd,be,bf,bg.......... and goes on.
I need by formula if possible, or macro .

Attached table sample data explained how to be listed.

Thanks in advance for any reply and help.
Regards,
turist