At my very first job in the 80s, my voicemail had a pin code for access. When I went to my next job, I got to pick my own code, so I used it again. And so on, and so on, and so on, all the way through my career I used that code, though at some point, I think I had to add a zero.
I mean, I guess we all do this in a sense, depending on how far down the digits you want to go … (Or was that the joke?)
But is it recursive?
Has anyone ever heard of a case where some stranger was able to get access to someone’s money via an ATM by guessing their PIN? I just don’t see how that would happen. Maybe a child or a spouse, but that’s a different problem.
I think my library card is the only 4 digit pin I use. All of my pin numbers (redundant, and IDGAF) are at least 9 - 13. Often, they are combinations of names and years that are significant to me, but not related to each other.
What stops me dead in my tracks are the machines that just have the numbers and not the letters!
It baffles me that the US is stuck on 4 digit pin numbers…
Mine comes from a certain area of science. But I’m not saying which one… 
1234 is apparently 11% of PINs, so, it would be the first I’d try were I of that bent. Add 1111 and 0000 to the list and you have almost a one in 5 chance to get it in three tries.
My goto PIN is a year of historical significance, but not to US history, and most Americans don’t recognize it. I looked at part of the list-- it’s not in the first 2000, and I kind of expected it to be, maybe around #1800 or so.
Did a search, and my computer didn’t find it in the whole 10,000, which was kind of surprising. But searches do go wrong.
No one would guess it on the first few tries, since it isn’t my birthday, or my dog’s name. Even if you were to try guessing just historical dates, you’re unlikely to hit it by guessing before you got locked out for bad passwords.
If I need a longer password, I use my Hebrew keyboard overlay, and pick a Hebrew word, and the password is whatever the layover corresponds to. If I picked a 3-letter Hebrew word, and the first letter overlays C, the second overlays Y, and the third overlays L, the password would be LYC (Hebrew goes right to left). That’s not a real example, because if I did that, it would be for a 5, 6 or 7 character password, but you get the idea.
I think there used to be 5 digit ones. But apparently in Europe some machines there only accept 4 digits? So I changed to 4 digits since we used to travel quite a bit
Mind you, the PIN is hardly the strongest or first line of defence!
Nope. Memorized. And also on a secure thumb drive in a mayonnaise jar on Funk and Wagnall’s back porch, too.
I just have the one, and like your first two, it was a PIN I was assigned by a bank, probably 30-35 years ago in my case, and like you, I kept it because I already had it memorized, also because it did have a pattern of sorts once you knew it.
To access my work system, I need three different codes:
- a 6-8 digit PIN that can be entirely numerical, and doesn’t have to change
- a 12-character password with at least one uppercase, lowercase, number, and special character. It has to change every 60 days, but fortunately just changing one character is good enough. I’ve been using the same first 9 characters forever, and only changing the last three. It’s got a nice, tight pattern on the keyboard.
- an 8-character RSA code that changes every 3 or 4 months which consists of numbers, lowercase letters (no uppercase!), and one special character. One time the special character was =, which was nice because I didn’t have to hit the shift key.
Once I’m inside the system, there are things I need the 12-digit password for, but not the other two.
But thirteen days from now, I’ll be retired, and I won’t need any of these anymore. 
I use my old college student ID#. Wrote it so many times I couldn’t forget it if I tried. If only four digits required I leave off the first of last digit.
Many years ago I had to change my PIN when I learned that some ATMs don’t accept a PIN that starts with a zero. Great, take a small search space and make up a pointless rule to reduce it even further. Mine was a MMDD date but now it isn’t.
I once read a Japanese comic strip where a guy suddenly gets a phone call from his ex girlfriend who asks him what his birthday was. Subsequent panels shows him happy she still thought about him. . . . . and that she had forgotten her PIN.
I know my wife’s ex boyfriend’s birthday.
For a while I used 2580 because it goes down the middle column.
When I’m at a gym or somewhere else that I have to choose a combination for a public locker, it amuses me to use 7734 from the childhood joke “upside down and backwards.”
I once had a bank which REQUIRED that PINs be a date in MMDD format. That reduces the search space from 10,000 to 366. FWIW 274 of the 366 begin with a zero.
I once had a randomly assigned number for my ATM card that had personal significance but was very obscure. My account was hacked anyway so I had to change it.
Don’t forget the Fibonacci Series: 1123
I think Readers Digest said the least likely PIN was 8068. I dont use it, but its clever.
I use a five-digit PIN – an old ZIP code – in various places. Sometimes I need a six digit PIN – the same old ZIP code with an extra digit. A while back, I was prompted to change that PIN; I broke it into a string of three two-digit numbers and reversed the order.