rep-n for all n other than 2, 3 Below are solutions for n = 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17 and 21
The extension below turns a rep-k to a rep-(k+10) for all k other than 6, 7 and 11 (see possible rectangles).
rep-n for n = 6, 7, 8, 9, 10, and all n >12 Since a 6x6 square can be made with four copies of this enneiomino it is clear that it is rep-(6k) for all k. The diagrams below show rep-n for n = 7, 8, 9, 10, 16 and 17.
The next diagrams show extensions from
rep-(3n+1) to rep-(3n+7) for n = 2 or n > 4rep-(3n+2) to rep-(3n+8) for n = 2 or n > 4rep-(3n+3) to rep-(3n+9) for n > 1