Minecraft Wiki:Sandbox

PACK.PNG SEED WAS FOUND!
As you might have already heard by now, we have finally managed to find the Minecraft world seed of the famous pack.png icon, but due to a rushed reveal, we haven't been able to make a proper announcement until now. Still, better late than never, so here goes! This 128x128 icon is considered to be one of the most iconic Minecraft images. It's been in the game for almost 10 years now and is still present to this day (in one way or another), but nobody ever knew where it came from, or which seed generated it. Until finally, after 8 months of hard work by 2 teams of Minecraft experts and other volunteers, the seed has been found on September 5th 2020 at 4:04AM UTC!

Here's everything you need to know to generate it yourself:
Minecraft version: [JAVA] Alpha 1.2.2 (don't forget to enable historical versions in the launcher!)

Seed: 3257840388504953787

Hill coordinates: X=116, Z=-31

If you need help with loading that seed, or want more details on how to replicate the icon yourself, here's a tutorial on how to do that: https://pastebin.com/CmsEKDev