Implicit sketching when the sketch tensor is rank-1. $T_x^{\left(t\right)}$ denotes the tensor embedding of order t:$T_x^{\left(t\right)}\left[a_{1\dots t}\right]:=\mathrm{\#}\left\{i_1<\cdots <i_t:x_{i_1\dots i_t}=a_{1\dots t}\right\}$, and $h_1,h_2\sim {\left\{-1,1\right\}}^{\left|\mathrm{\Sigma }\right|}$ denote sign hashes. e₂ = [0, 1, 0, 0] is the indicator corresponding to the appended character “C.”