Tuesday, March 31, 2020

Concentric Rectangles

I'd like to blame the fact I'm stuck indoors avoiding the Coronavirus for this one, but realistically I'd have probably found the time to solve this anyway, given that I lead such an exciting life:


It's an awful photo, but here's the gist of it. Imagine a 7x9 pentomino rectangle (with a little 3-cell hole) inside a 13x21 hexomino rectangle, inside a heptomino rectangle I can't remember the dimensions of and can't be arsed to count, all surrounded by the octominoes (plus 8 holes) in a whopping 47x85 rectangle. And that's what I spent an entire afternoon doing. Well, two sittings with a break for dinner in the middle.

It would maybe have been a bit nicer if I'd started with a central monomino and worked my way up through all polyomino sizes, a la Karl Wilk's Polyominium, but there didn't seem to be a way of doing it that yielded such nice symmetrical layers like this. It's difficult to wrap a pentomino rectangle around a hole big enough for just the tetrominoes, let alone anything else.
In fact, when I had the original idea that became this, it was born out of the fact I'd built a hexomino pattern that just happened to be able to fit the 7x9 rectangle inside.

A sort of precursor solution found way back.
Peeps with a keen eye will have spotted that the pent-, hex- and heptomino sections of that early solution are totally different to the ones this time round - more a testament to how bored I was than anything else.

Fun fact about the 7x9 pentomino solution: when the triomino hole is vertical there are 360 possible solutions, whereas with the horizontal hole there are a mere 150 (excluding rotations, reflections and all that jazz.)

Here's the full solution drawn up so you can actually see where one piece ends and another begins:

And there's a little voice inside me saying "What about a layer of nonominoes?" but realistically I'm not going to be able to do that without a physical set of them and that ain't gonna be cheap. Besides, there's not a flat surface in my house big enough to hold all those pieces.

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