Question 554879
If you have consecutive even numbers, each one is equal to the previous one plus 2.
That could be written as {{{a[n]=a[n-1] +2}}} or {{{a[n+1]=a[n] +2}}} .
If your first term is {{{a[1]}}}, the second would be {{{a[2]=a[1]+2}}} .
The third one would be {{{a[3]=a[2]+2+a[2]=a[1]+2+2}}}
The fourth one would be {{{a[4]=a[1]+2+2+2}}}
The fifth one would be {{{a[5]=a[1]+2+2+2+2}}}, and so on.
Each time you calculate the next term, you are adding 2.
When you get to the nth term, you have added n-1 times the number 2, so
{{{a[n]=a[1]+2(n-1)}}}