Counting License Plates | Hacker News Reader

Counting License Plates

alexmolas.com

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The writer & comedian Richard Herring devised a fairly complete set of rules for this, calling it Consecutive Number Plate Spotting (CNPS). It's amusing, https://www.richardherring.com/cnps

Found his blog entry when he found #999. From 19 years ago(!). https://www.richardherring.com/warmingup/26/7/2004/index.htm... . Took him 20 months, and that was with notes about where he saw cars with upcoming numbers.

I like these kinds of games for long car drives.

My favourite (I'm in the UK, where licence plates generally have the form XX 123 XXX where Xs are letters and 123 is three numbers) is to make the shortest word possible by adding additional letters to the XXX letters while keeping the original letters in order. (e.g. if the letters were FTU you could do FORTUNE but not TURF). Even better when there's more than one of you and you just say how many extra letters you've added to make a word until you both agree that you've got as few as possible, then reveal each word.

Another one I like is to get from one to as high a number as possible using the three numbers, e.g. if you have 136 you go:

  1 = 1
  2 = 3-1
  3 = 3
  4 = 3+1
  5 = 6-1
  etc.

That game doesn't last long though...

Sometimes I let myself cheat and use factorial (i.e. 3! = 3x2x1 = 6)

Good car games for kids that we use:

ABC animals - you go around the card one-by-one naming an animal that starts with A, then B, then C etc. Variants on this are foods, boys names, girls names etc.

Word association for older kids can be fun too.

But that's not the format for UK licence plates at all!

They are XX11 XXX. The initial 2 letters are the region and the following 2 numbers are the year. The second half of the year is the number plus 50. So, eg 2022 car might be HA22 ABC or HA72 ABC.

Edit: I said UK licence plates but that's not strictly accurate. Northern Ireland has a different system.

Technically, that's not true either! That's the current format, previous formats (still legal and transferable/usable) have included XN, XNNXXX, XXXNX, and others!

It was pretty close, hardly "not at all"! You're right that the new format has two numbers - three numbers was from the old ABC 123 A format.

I’ve been playing a game with license plates as well, for many years now. It’s quite simple: combine the numbers found in the license plate such that they form a valid equation. Regular binary operators are allowed, exponentiation is available and parentheses can be placed arbitrarily.

For example, 6827 can be 6 + 8 = 2 * 7. 238 is 2^3 = 8. 9033 can be 9 ^ 0 = 3/3 (among others).

It’s simple and quick enough to do on the fly, in traffic, but surprisingly fun even long term.

I also play this game, and Lev Landau used to play it as well Apparently, there's a universal solution for the game [0]

[0]: https://www.johndcook.com/blog/2019/02/02/landau-kolmogorov/

Ontario plates run from AAAA-001 - ZZZZ-999 and are about to hit D series. https://www.licenseplates.cc/ON

I'm surprised when states have that many consecutive letters, because the number of "potential words" you have to flag and avoid become larger and larger, the "NAG 365" isn't even close to the worst case, especially if you have four letters.

> My ultimate goal was to observe all 10,000 license plates before my time on this Earth is up - which I predict to be in around 50 years.

Good news: the chance of this coming to pass is the same whether you play or not!

For around a decade Arizona had license plates in the format AAA0000 that were being distributed in order, but some time before they finished the ones starting with C they switched to another system. That system had 7 alphanumeric characters in an apparently scrambled order but with an unusual high number of repeated characters. Now they've changed again to 6 scrambled alphanumerics.

Is the number randomly generated? If not, then I think the probability is wrong since there are many series of numbers that have never been issued

The numbers are generated in order. They started with 0000-BBB, then 0001-BBB, and it'll continue until 9999-ZZZ. We're currently around MDB. This means that it's a good approximation to assume all the numbers are equally probable.

Ah ok, wasn't sure if the numbers incremented first or the letters

this would be much easier in a state that was AAA-#### as there'd be a much more even distribution of numbers

California is relatively close with #AAA###, I remember using spotting new first # as an indicator as to how many cars had been bought.

Yep, my parents purchased a car in 1978 that was still on "NNN AAA". Then our next car was a 1986 model, and I believe it was a "1 AAA NNN" series. By 1993, I purchased a car with ridiculous vanity plates, so I immediately pulled them off and registered normally, receiving a "3" series plate.

When I drove around California with my girlfriend, she would spot out-of-state plates, announce the state, and then punch me on the upper arm while I was driving, usually on the freeway.

As a man, I was not about to punch a woman, whether it was part of a game or not, and after a while, I developed a significant bruise on my right arm, and I don't think that was a fair or fun pastime.

I'm old enough that I remember riding in cars and having friends who liked to play "punch buggy". Every time they saw a VW Beetle, they'd punch me in the arm. They quickly learned that I would punch them back in the arm much harder than they had punched me. They quickly stopped playing that game with me.

Jumping on the license plate topic, here’s a post I put up in 2022 on the distribution of letters/numbers in Massachusetts plates

https://blog.charliemeyer.co/mathematical-theory-of-license-...

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