English
If there exists k with p(k) and n ≤ k, then n ≤ nth p (count p n).
Русский
Если существует k, such что p(k) и n ≤ k, то n ≤ nth p (count p n).
LaTeX
$$$$ \\exists k:\\, p(k) \\land n \\le k \\Rightarrow n \\le \\mathrm{nth}(p, \\mathrm{count}(p,n)). $$$$
Lean4
theorem le_nth_count' {n : ℕ} (hpn : ∃ k, p k ∧ n ≤ k) : n ≤ nth p (count p n) :=
(le_csInf hpn fun _ => And.right).trans (nth_count_eq_sInf p n).ge