In this paper, there are two formulations of regret at time $n$:
$R_n=n\mu^*-\sum_{t=1}^{n}E[\mu_{I_{t}}]$
$R_n=\sum_{i=1}^{K}\Delta_iE[T_i(n+1)]$
Where
$\mu_i$ is an expected value of some unknown distribution $v_i$ of arm $i$ (distribution that generates rewards)
$\mu^*=max\{{\mu_i}\}$
$I_t\in\{{1, ..., K}\}$ is the action taken at time $t$
$\Delta_i=\mu^*-\mu_i$
$T_i(t)=\sum_{l=1}^{t-1}1_{\{I_l=i\}}$ is the number of times arm $i$ was pulled strictly before time $t\geq2$
Can someone show why are they equivalent?