Skip X Columns In Formula Reference When Dragging Across Columns

How do you make the Autofill function increment in blocks, e.g. instead of increment 1,2,3 increment 1,8,15 inthe following example: I have a 2 worksheets, one with days of the year across columns and values down rows, and another that summarises the sum of the corresponding days in weeks, so I have 365 columns in sheet 1 and 52 columns in sheet2. Everytime I update the sum range i cannot autofill it in the summary worksheet, as A1:G1 autofills to B1:H1, but I want it to increment to H1:N1.