Post #1098408

@rnd@toot.cat @jim_easterbrook@mstdn.social good example! A friend of mine teaches university-level mathematics, and has been known to set the question "2^29 is a number with 9 distinct decimal digits. Which digit is missing?" and the challenge is to answer it using first-year number theory results without just calculating what the number actually looks like. As a lifelong low-level programmer, I have all the powers of 2 up to 2^32 solidly memorised, so when he mentioned that question, I didn't _have_ to calculate – I recited "536870912" straight off the top of my head, and (from practice on Sudoku) also immediately knew 4 was the digit I hadn't seen. But I'd never _noticed_, even when memorising that number, that it had nine distinct digits. I recited it out loud and then said "oh yeah! I never noticed that before!"