the hundred chart · primes picked out in colour
Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.
Three sizes in one archive — from a sheet on the fridge to a poster on the wall.
Each row is one ten. The primes are picked out in colour.
Look at the columns: nearly every prime sits in four of the ten.
Apart from 2 and 5 themselves, every prime ends in 1, 3, 7 or 9 — any other ending divides by 2 or 5.
So six columns out of ten are almost empty. You can see it, and it’s no coincidence.
Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 3 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.
