[carlkcarlk]

Yes, the article figures that with a limit of 64GB of memory, with simple nested loops, you could only loop about 10^(165 billion) steps.

To get 10^^15 steps, the article assumes "any amount of zero-initialized memory". (It calls that assumption "unrealistic but interesting".)

[kryptiskt]

You can hook it up to a cloud service, say an S3 bucket, and allocate storage space as needed. Then it fulfills the condition of unbounded memory, at the small price of unbounded cost. But it will not be a problem during your lifetime.

If you are cloud-averse, you could do the same with networked storage on your local LAN and just connect more disks when it's running out.