Admissible sequence of Steenrod squares
= Admissible sequence of Steenrod squares
{title2=$i_j\geq2i_{j+1}$}
An index sequence obeying the displayed inequalities represents an admissible product $\operatorname{Sq}^{i_1}\cdots\operatorname{Sq}^{i_r}$. Its degree increment is the sum of the indices. The <Adem relations> rewrite every square monomial in terms of admissible ones, whose <Steenrod excess> controls universal instability.