What does "in sequence" mean?

Sequentially, one after another.

In sequence

Common synonyms include: adjacently, alternately, consecutive, forward sequencing, in order, in succession.

adv

adv ·Rare ·Advanced level

Adverb

1
Sequentially, one after another. dated, not-comparable, rare
"He built the house brick by brick in sequence."

"He built the house brick by brick in sequence."

By surface analysis, in + sequence. Possibly a confusion from Latin īnsequēns (“following, pursuing, next”, present active participle).