Exotic Structures of LEGO Bricks

by Ingo Althöfer, March 05, 2014; Update March 11, 2014;


Disclaimer: LEGO is a trademark of the LEGO Group. My investigations on exotic structures are neither sponsored nor supported nor authorized by the LEGO group.


Danish mathematicians Mikkel Abrahamsen and Soren Eilers have written a very nice paper, entitled "On the Asymptotic Enumeration of LEGO Structures". It was published in the journal Experimental Mathematics 20 (2011), 145-152.

Their formal definition of "contiguous structure" does not include the "exotic" (topologically non-trivial) examples shown on this site.



Chain-Like Structures




The building blocks/rings.


Two rings intertwined.


Three rings intertwined.



Ring around a Bone









Bricks in a Chamber




Open chamber.


Closed chamber.






Observe that the two structures with two bricks in the closed chamber can not be smoothly converted into another.






Observe that the two structures with three bricks in the closed chamber can not be smoothly converted into another.

*** Conjectures ***

1. Almost all (contiguous) large structures are NOT simply connected.

Here "simply connected" is meant in the topological sense.

An example: Building random planar structures from 1x3-bricks step by step (with equal distribution for the "docking" places of each new brick) results in a first hole after typically 6 to 30 bricks. The collage below shows a case where the first hole occured with the tenth brick.





2. Almost all (contiguous) large structures have many "nice" handles.

Here, "nice" is meant with respect to our intention to couple two (or more) structures together like in the chain-structure photos on top of this site. Observe that not all handles in LEGO structures allow chain-like connections. The blue structure in the next photo is a simple example of a bad handle.



3. Almost all large structures are not contiguous structures in the spirit of Abrahamsen and Eilers.

When two structures with nice handles are given, they can be in coupled state. The more nice handles the structures have, the more likely it is that they will occur in coupled state.




These conjectures are meant also for (3-dimensional) structures which are made of 4x2-bricks only.



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