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arXiv · 2401.13356

Properties of Steiner triple systems of order 21

Grahame Erskine·Terry S. Griggs
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Abstract

Properties of the 62,336,617 Steiner triple systems of order 21 with a non-trivial automorphism group are examined. In particular, there are 28 which have no parallel class, six that are 4-chromatic, five that are 3-balanced, 20 that avoid the mitre, 21 that avoid the crown, one that avoids the hexagon and two that avoid the prism. All systems contain the grid. None have a block intersection graph that is 3-existentially closed.

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Grahame Erskine, Terry S. Griggs. 2024-01-24. Properties of Steiner triple systems of order 21. https://arxiv.org/abs/2401.13356

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