Find and Replace

I have a spread sheet with over 3360 rows and in column a I have a number that goes up by 1 every 7 rows.
So The column looks like:

1
1
1
1
1
1
1
2
2
2
2
2
2
2
3...


I have to change all those numbers to match a new set of numbers. So for an actual example from my spread sheet 145802 has been changed to 146522, 145803 changed to 146523, and so on, each one just add 1 more
Currently the way I am doing it is using find and replace. This way I have to do a find a replace 480 times but if there is another more efficient way I would appreciate the advice a lot! As it will save me a lot of time down the line because I will be doing this same process 4 more times

Thanks for any help you can offer, and if something needs better explaining, I will do my best to explain a little bit better.
Thank you!