Find the nth term of this quadratic sequence - 1,8,23,44,71,104

Difference between each term : _

9 15 21 27 33

second difference:-

6 6 6 6

Dividing this by 2 = 3

so first part of nth term is 3n^2

Substituting n into 3n^2 : -

= 3 12 27 48 75

Now take these values from the original numbers:-

-4 - 4 - 4 - 4 - 4

So the required nth term is 3n^2 - 4