MrCollatz

Take any whole number. If it's even, halve it. If it's odd, triple it and add one. Repeat. The Collatz conjecture says you will always reach 1 — and no one has ever proved it. MrCollatz lets you watch it happen with numbers far too big to do by hand. • Start from a random number of 30 to 200 digits, or type in your own • Run it all the way, or step through one move at a time • Watch the trajectory charted live on a log scale, with the peak marked • Six graph styles: area, line, bars, points, stepped and spiral • See the step count, peak size, and how many 3n + 1 and n ÷ 2 moves it took • Auto mode tests number after number and keeps a running total Random starting numbers always leave remainder 3 when divided by 4, which tends to give the longest climbs before the fall. And if a number ever refuses to come down, MrCollatz will tell you. You may have disproved a famous conjecture — show it to a maths person. No ads, no accounts, no tracking. Everything runs on your device.