Question

What is a2? ai + 1=ai +1 a0=0 ?

Answer 1

If a₀ = 0, and $a_{i + 1} = a_i + 1$, then

a₁ = a₀ + 1 = 0 + 1   ⇒   a₁ = 1

and

a₂ = a₁ + 1 = 1 + 1   ⇒   a₂ = 2