Well, I won't do all the process to render the html. Can you post something easier to read? You could just get a SELECT with the results you need.

Here's a sligthly faster version than the original one. I'm not sure what happens if we add a proper holidays table.
I tried by adding a filtered index to...

A simpler solution, assuming that you can only get zeros and ones.

WITH SampleData AS (
SELECT * FROM (VALUES
(1, 62, 0),(2,...

EDIT: This is a worse version of Lynn's code. I didn't see it before posting.

How about preventing any updates done to table_a by other connections?

[code...

Here's another possible solution, pure brute force.

WITH
E(n) AS(
  SELECT n FROM (VALUES(0),(0),(0),(0),(0),(0),(0),(0),(0),(0))E(n)
),
E2(n) AS(
  SELECT a.n FROM E a, E b

Thank you for the feedback....

Did you find a real-world problem with this functionality? Or were you experimenting?