How to get interspersed sequential numbers?

I wish to add a sequential numbers to 1 column at various rows, i.e., 10, 13, 15 the rows in between will have other numbers e.g.,


I want 510066 to go in the next blank cell in the same column.

When you say “at various rows”, and from the example provided, it appears that the sequential numbers are to be randomly interspersed with other numbers. There does not appear to be a pattern to the rows where the sequential numbers are to occur. Without a pattern, it is impossible to using either a function or macro to produce a solution. Something like the =RANDBETWEEN() function might be useful if the sequential values occur every set number of rows i.e., a value between 1 and 4.

Correct, the only pattern to anything is the sequential number, as in the example, there may be 2 or 20 cells between the sequential number, the only way to do this is last thing to be done is to add the numbers in this column and using sort than cell+1 etc. which i dont want to do as it will take much longer to do.
there will be about 2500 rows and i would like to do this line for line.