Ask HN: Why do parking tickets across lots of cities follow a similar # pattern?

#1

Post by davidhegarty » Mon, May 18, 2015, 8:35 PM UTC

We noticed something interesting as we were looking at parking ticket numbers.

The sequence of parking ticket numbers follows a similar pattern across lots of different cities.

We thought it was because cities shared a similar software vendor... but it looks to be more extensive than that.

Anyone have any ideas why a large number of cities have the following parking ticket sequence:

827778501 (+11) 827778512 (+11) 827778523 (+11) 827778534 (+11) 827778545 (+11) 827778556 (+11) 827778560 (+4)

...and then continues to add '11' six times, and then adds a '4', and keeps repeating.

Is there a reason for this? Is it a common sequence in other places too?

Re: Ask HN: Why do parking tickets across lots of cities follow a similar # pattern?

#2

Post by madcaptenor » Tue, May 19, 2015, 1:37 PM UTC

The last digit may be a check digit. In particular, it might be the remainder upon dividing the number that the other digits make by 7. For example 82777850 divided by 7 leaves a remainder of 1. Some examples of this check digit scheme:

http://nrich.maths.org/2036 http://www.cbp.gov/sites/default/files/documents/in_bond_che... (with a clunky implementation) http://www.con-way.com/en/tools_pricing/freight/fr_tools/tra...

Re: Ask HN: Why do parking tickets across lots of cities follow a similar # pattern?

#3

Post by davidhegarty » Tue, May 19, 2015, 4:26 PM UTC

madcaptenor wrote: post #2

The last digit may be a check digit. In particular, it might be the remainder upon dividing the number that the other digits make by 7. For example 82777850 divided by 7 leaves a remainder of 1. Some examples of this check digit scheme: http://nrich.maths.org/2036 http://www.cbp.gov/sites/default/files/documents/in_bond_che... (with a clunky implementation) http://www.con-way.com/en/tools_pricing/freight/fr_tools/tra…

BINGO!!! You da man. That's seems to work for all my examples.

Thanks!