Tangle

Fig. 1: Tangle class 1, with 4 links. There is 1 unique tangle, up to isomorphism. This tangle is unique among all classes in that it is the only example with more than two (four) consecutive ones in the bit string.
Fig. 2: Tangle class 2, with 8 links. There is 1 unique tangle, up to isomorphism.
Fig. 3: Tangle class 3, with 12 links. There are 3 unique tangles, up to isomorphism.
Fig. 4: Tangle class 4, with 16 links. There are 7 unique tangles, up to isomorphism.
Fig. 5: Tangle class 5, with 20 links. There are 31 unique tangles, up to isomorphism.
Fig. 6: Tangle class 6, with 24 links. There are 138 unique tangles, up to isomorphism.
Fig. 7: Tangle class 7, with 28 links. There are 808 unique tangles, up to isomorphism.
Loops of length 4n on square grid that turn at each step and return to start in original direction, OEIS:A000644.

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