Hello, Anna!

The problem is not stated clearly.

Are we concerned with the last (rightmost) digit?The sequence can start with any number (or so I think).

The pattern is: add 7 ... but if the last number is 2, 1 or 0, add 17.

. . or the last two digits? . . . or what?

If we are interested in only thelast(rightmost) digit,

. . then the above condition is redundant, isn't it?

Whateverthe last digit, we add 7.

The cycle repeats itself every ten digit.

If we are concerned with the lasttwo-digits,

. .

and we still have a ten-number repeating cycle.

So what was the question?