Three-Pivot Drill

You now have three pivots: 35, 49, and 70. Every other 7s fact sits within two sevens of one of them. The drill is to practice the rebuild until it beats raw recall.

Set one rule: three seconds or hint. If a fact does not surface in three seconds, say the nearest pivot out loud and count to it. Run this in dead moments — waiting in line, boiling the kettle. After a few days the pivots fire on their own, and the whole table collapses into a handful of small adjustments.