The average<span> of the terms of a contiguous subsequence of any arithmetic progression is the </span>average<span> of the first and last terms. To see this, notice that if you remove </span>25<span> and </span>41<span> from your sequence, then the </span>average<span> of the remaining terms is still given by the </span>average<span> of the extreme terms 26+402=33 .</span>
