1. ## What pattern is this? add 7 or 17

Could anyone please assist me. I have been trying to figure out what this pattern in called. Or if anyone knows any info on it I would appreciate the help. It can start with any number (or so I think). We will start with 1.
The pattern is add 7 but if the last number is 2, 1 or 0 add 17.

1, 18, 25, 32, 49, 56, 63, 70, 87, 94
or
2, 19, 26, 33, 40, 57, 64, 71, 88, 95

What I see is the last digit of each number is only used 1 time as the last digit. As well as the first digit. None repeat them selves.

Would they repeat after 1000 cycles.

And help is appreciated

Anna

2. Hello, Anna!

The problem is not stated clearly.

The pattern is: add 7 ... but if the last number is 2, 1 or 0, add 17.
Are we concerned with the last (rightmost) digit?
. . or the last two digits? . . . or what?

If we are interested in only the last (rightmost) digit,
. . then the above condition is redundant, isn't it?
Whatever the last digit, we add 7.

$\text{The sequence is: }\;\underbrace{1, 8, 5, 2, 9, 6, 3, 0, 7, 4}, \;\underbrace{1, 8,5,2,9 \hdots}$

The cycle repeats itself every ten digit.

If we are concerned with the last two-digits,

. . $\text{we have: }\;\underbrace{01,18,25,32,49,56,63,70,87,94},\;\u nderbrace{01, 18, 25, 32, 49 \hdots }
$

and we still have a ten-number repeating cycle.

So what was the question?

3. ## 7 17

Apologies if the ? was unclear, as it is not clear to me how to explain it.
I thank you for the help.

I was wondering if this was a sort of system like luhn or mod 10.

Thank you agian.