How to create a sequence of numbers with repeat and increment at intervals in google sheets

I need a single cell formula to create a sequence of numbers with a limit in Google Sheets as shown in the image.

3 rows repeat the value

then Increment by 5

>Solution :

Use this formula, you can adjust the Sequence() and REPT(rg&",",3) parameters to your need.

In this example Sequence(number_of_unique_numbers,columns,start_at,increment_by)

And REPT(rg&",",Repeat_N_times)

=ArrayFormula(FLATTEN(SPLIT(BYROW(SEQUENCE(3,1,5,5), 
 LAMBDA(rg, IF(rg="",,REPT(rg&",",3)))),",")))

Used formulas help
ARRAYFORMULA – FLATTEN – SPLIT – BYROW – SEQUENCE – LAMBDA – IF – REPT