English
Let α be a semiring. An element a ∈ α is odd if there exists k ∈ α with a = 2·k + 1.
Русский
Пусть α — полукольцо. Элемент a ∈ α нечетный, если существует k ∈ α such that a = 2·k + 1.
LaTeX
$$$\\mathrm{Odd}(a) \\coloneqq \\exists k:\\alpha,\\ a = 2 \\cdot k + 1$$$
Lean4
/-- An element `a` of a semiring is odd if there exists `k` such `a = 2*k + 1`. -/
def Odd (a : α) : Prop :=
∃ k, a = 2 * k + 1