For each prime number $p \neq 2$, $17$, what is the number$$N_p := \text{card}\{(x, y) \in (\textbf{F}_p)^2 : 2y^2 = x^4 - 17\}?$$I need this result, but unfortunately I am not a number theorist. Could anyone provide me a reference/supply a computation? Thanks!