By convention, the first term of a sequence starts with n = 1 instead of n = 0. This is so n = 1 matches with 1st, n = 2 matches with 2nd, and so on.
In contrast, the y intercept always occurs when x = 0. So something like y = 3x+5 has a y intercept of 5 when you plug in x = 0.
An arithmetic sequence like f(n) = 2n+7 has its first term when n = 1. So the first term would be f(1) = 2(1)+7 = 9 instead of 7 as Hank claims.
