I was playing around with some slippery pentagons and ended up with this pattern. I was trying to get them to squeeze together a little better and was having a bit of difficulty. I didn't look carefully enough to see that the gaps were very different. I was focusing on the lines of pentagons and I missed that the gaps changed half way along the line. It's interesting how the regularity can fool you into thinking that it's more regular than it is. Perhaps it's not that subtle and I was just playing after a long day of work.