Well gosh darn it we didn’t invent GPUs just to mine bitcoins!
"Exponential" is an anagram for "More processing power won't save you".
Then why does GPU stand for Bitcoin Processing Unit?
At a minimum you could include all 2-character combos? Or even just a common subset, maybe the top 100 or those appearing in 1%+ of the OED. And MNIST itself is kind of limiting since no one was trying to write numbers "artistically".