# Missing formula! [closed]

I am doing a project on group association schemes, in particular looking at the structure constant $$p_{KL}^M = \#\{(x, y, xy) : x \in K, y\in L, xy \in M\}$$ where $K, L$ and $M$ are conjugacy classes.

I have been given a formula to help me, but cannot get hold of it anymore! It has this expression on the right-hand side: $$\sum_{\chi \in \DeclareMathOperator{\irr}{Irr} \irr(G)} \frac{\chi(x) \chi(y)}{\chi(xy)}$$ Does anyone recognise this?

## closed as off-topic by user10534, Carlo Beenakker, Andrés E. Caicedo, Yemon Choi, Felipe VolochAug 29 '13 at 23:00

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• "This question does not appear to be about research level mathematics within the scope defined in the help center." – Derek Holt, Carlo Beenakker, Andrés E. Caicedo
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