Abstract
Connor [3] has shown that the relations among the parameters of the triangular association scheme themselves imply the scheme if $n \geqq 9$. This result was shown by Shrikhande [6] to hold also if $n \leqq 6$. (The problem has no meaning for $n < 4$.) This paper shows that the result holds if $n = 7$, but that it is false if $n = 8$.
Citation
A. J. Hoffman. "On the Uniqueness of the Triangular Association Scheme." Ann. Math. Statist. 31 (2) 492 - 497, June, 1960. https://doi.org/10.1214/aoms/1177705914
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