Sieve of Fortune — Your Daily Lucky Number, With the Mathematics to Prove It

Watch the sieve work

Unlike the Sieve of Eratosthenes, which removes numbers by their value, the lucky-number sieve removes them by their position in the surviving list. Whatever remains after every pass is lucky. The number above survives — watch it happen.

How your number is chosen

Six facts about the present moment, each weighted by a lucky number, add up to one position in the sequence. Deterministic, transparent, and different tomorrow. Here is a real ledger from the extension:

What's inside

The real sequence

The Ulam sieve is computed live in the popup — no lookup tables, no fakery. Verified against the published sequence (OEIS A000959).

Reasoning shown

A ledger prints every factor and weight, ending in the modular arithmetic that lands on your number's position.

Lucky prime badges

When your number is both lucky and prime — like 7, 13, 31 or 37 — it earns a badge, along with palindromes.

Animated sieve

Every open replays the elimination passes over the numbers 1–63, so the definition is something you watch, not just read.

A fact a day

Sixteen rotating facts from number theory: twin luckies, the Goldbach analogue, why 13 is mathematically lucky after all.

Make it yours

Add your name and its letters join the arithmetic — your number diverges from everyone else in your city.

The mathematics

Lucky numbers were introduced in 1956 by Gardiner, Lazarus, Metropolis and Ulam. Begin with the natural numbers and strike out every second one. The next survivor after 1 is 3, so strike every third remaining number. The next survivor is 7 — strike every seventh. Continue forever. What survives is the sequence

1, 3, 7, 9, 13, 15, 21, 25, 31, 33, 37, 43, 49, 51, 63, 67, 69, 73, 75, 79, …

Remarkably, these numbers behave like the primes in several deep ways: they thin out at the same asymptotic rate, twin luckies appear about as often as twin primes, and a version of Goldbach's conjecture extends to them — all from a sieve that never once looks at what a number is, only where it stands.

Privacy

Zero permissions. The extension requests nothing from Chrome — no tabs, no history, no location access.
Nothing leaves your machine. All arithmetic runs locally in the popup. There is no server, no analytics, no tracking.
Your name stays yours. If you personalise with a name, it is stored only in the extension's own local storage and never transmitted.
“Location” is just your timezone. The place factor is your system timezone name — the same string every website can already read — folded into a single small number.