The singularity of this license plate was almost lost on me. I noticed it as I was pulling out of my parking space, and I thought: “Hey, ‘Civ 104’, like the 104th entry in the Civilization series! Boy, it’ll be a long time before they get to that one. Kind of like that other hypothetical Civ game, the one they’ll call ‘Civ CIV’, because it’ll be the one where the number of the game is ‘CIV’ in Roman numerals…”
Then I started pulling back into that parking space (luckily it didn’t take me too long to think all that stuff), so I could get a picture. CIV 104! It’s that number! CIV! 104! Oh my gosh! Roman numerals!
Since I saw this license plate a couple days ago, I’ve been wondering: How many license plates, in the Iowa style (3 letters, 3 numbers), have this property? And how could I answer that question with a minimum of effort? Yes. This is the kind of thing I do for fun.
The brute-forcest way to do it would be to convert every decimal number from 001 to 999 into Roman numerals, and see which Roman numerals have three “digits”. That’s doing 1000 checks, though! A slightly less brutish method would be to convert every possible three-digit sequence of I, V, X, L, C, and D into decimals—that would be only 216 checks. Because M couldn’t appear in any of these license plates, right?
Well, no. For example: CMI 901. And what about the sequence IM? Is IM a legal Roman numeral? That’d be how you write 999, right?
Well, no. 999 is CMXCIX. I figured this out when I checked this big list of Roman numerals. And then I had yet another idea.
I pasted that list into Inform, and then I wrote a quick little rule to pull out the 3-digit Roman numerals. The complete Inform 7 source for my project is here, but this is the important part:
This returns a list of 62 possible license plates, which without further ado I reproduce here:
III 003 VII 007 XII 012 XIV 014 XVI 016 XIX 019 XXI 021 XXV 025 XXX 030 XLI 041 XLV 045 LII 052 LIV 054 LVI 056 LIX 059 LXI 061 LXV 065 LXX 070 XCI 091 XCV 095 CII 102 CIV 104 CVI 106 CIX 109 CXI 111 CXV 115 CXX 120 CXL 140 CLI 151 CLV 155 CLX 160 CXC 190 CCI 201 CCV 205 CCX 210 CCL 250 CCC 300 CDI 401 CDV 405 CDX 410 CDL 450 DII 502 DIV 504 DVI 506 DIX 509 DXI 511 DXV 515 DXX 520 DXL 540 DLI 551 DLV 555 DLX 560 DXC 590 DCI 601 DCV 605 DCX 610 DCL 650 DCC 700 CMI 901 CMV 905 CMX 910 CML 950
If you don’t think the series III 003 – XCV 095 should count, because you hate initial zeroes, the number of license plates that meets your fascist standards is 41 instead.
Thank you for your interest.