Explanation:
you really need help with that ? it is all already given in the problem description. you only need to do the 6 little calculations (anyways adding 6). what is the problem ?
a1 = 7
a2 = a1 + 6 = well ? ... ... ... 13, of course
a3 = a2 + 6 = 13 + 6 = weeeeelllll ?
a4 = a3 + 6 = 13 + 6 + 6 = weeeellll ?
a5 = a4 + 6 = 13 + 6 + 6 + 6 =
a6 = a5 + 6 = 13 + 6 + 6 + 6 + 6 =
I am really not doing your very basic and just "mechanical" work of doing simple calculations in your head or on your calculator.
I help you, when you have a problem understanding the issue, but not when you ask me to do your pure "mechanical" job that every elementary school student can do easily.
to help with the understanding, such a sequence (using this example) can then be described and every element calculated by
a(n) = a(1) + 6*(n-1)
so, for example
a20 = 7 + 6*19 = 121
so, and now that you truly understand the concept, just use your calculator (if you truly cannot do that in your head) and do your job.