[alexander_busek]

I was thinking of “Gateway” and the Heechee.

Nope, "The Sentinel" predates every other similarly-themed story by decades.

Regards,

[BenLurkin]

Understood.

Pohl’s concept was not groundbreaking, but the character of the artifacts in his novels, I believe, is closer to what the author of this so-called “equation” is anticipating.