# What pattern is this? add 7 or 17

• Aug 23rd 2008, 11:22 PM
selvol
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
• Aug 24th 2008, 04:10 AM
Soroban
Hello, Anna!

The problem is not stated clearly.

Quote:

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?

• Aug 24th 2008, 04:30 PM
selvol
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.