First Chern class formula for a symplectic blowup ($c_1(T\tilde{X})={\pi }^{\ast }{c}_1(TX)-(n-1)\mathrm{PD}[E]$)

For a symplectic blowup of a $2n$-dimensional symplectic manifold, the displayed formula gives its First Chern class. The exceptional divisor has normal bundle $\mathcal{O}(-1)$; the discrepancy coefficient is $n-1$. In dimension four it is one.