Take a look at ARRAY LAYOUTS FOR COMPARISON-BASED SEARCHING. TL;DR there are schemes like this called "Eytzinger" and "van Emde Boas".

https://arxiv.org/ftp/arxiv/papers/1509/1509.05053.pdf

The topic of arranging keys like this within index pages (or maybe elsewhere) has come up on the pgsql-hackers mailing list before:

https://www.postgresql.org/message-id/flat/3B774C9E-01E8-46A...