Identify the Progression 1 , 7 , 13 , 19

This is an arithmetic sequence since there is a common difference between each term. In this case, adding ${\displaystyle 6}$ to the previous term in the sequence gives the next term. In other words, ${\displaystyle a_n=a_1+d(n-1)}$.

Arithmetic Sequence: ${\displaystyle d=6}$

This is the formula of an arithmetic sequence.

Substitute in the values of ${\displaystyle a_1=1}$ and ${\displaystyle d=6}$.