Cell referencing a Row plus a number

I have a huge multi-tab spreadsheet that I would like to reference a series of cells. An example, on Tab1 have the following formula in cell A1. =sum('tab2'!A1:A10)

Now I want to B1 to sum up tab2 A11:A20 without having to recreate the formula 100 times for Columns B - RRR.

I want an automated way to copy a paste or click and drag the formula across all of the rows to have it calculate the sum ten 10 cells below the previous 10 cells that it summed in the previous cell.

Any help woudl save me hours per month!!!