OccurrencesOf213

Triples i < j < k with p(j) < p(i) < p(k).

OccurrencesOf213(p)

Domain: Permutation statistics

Details

• Defined over `Permutation` as an expression in `_x`, evaluated by compute-engine — the definition IS the implementation.
• Takes a `Permutation`, and also a bare list of integers: this reading compares entries with each other rather than with their positions, so it stands on any sequence.

Examples