1, 12, 123, 1234.....1234567890

Question

Can someone help me with the arithmetic formula for these numbers? If you can provide the code it would be helpful as well.
Using Fortran 95 Plato.

Answer 1

0*10 + 1 = 1
1*10 + 2 = 12
12*10 + 3 = 123
123*10 + 4 = 1234
1234*10 + 5 = 12345
12345*10 + 6 = 123456
123456*10 + 7 = 1234567
1234567*10 + 8 = 12345678
12345678*10 + 9 = 123456789
123456789*10 + 0 = 1234567890

You can use this logic with any programming