Question

how to find a sequence with 3n2​

Answer 1

Let $\green{n => 1}$

So, $3n^2 => 3×1 => 3$

Similarly, Taking $\green{n => 2}$

$3n^2 => 3×(2)^2 => 3×4 => 12$

Taking $\green{n => 3}$

$3n^2 => 3×(3)^2 => 3×9 => 27$

Therefore, Required AP (sequence) is $\orange{3 , 12 , 27 ,........}$