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Lucas Primes Generator

Scan the Lucas sequence and list every index where the Lucas number is prime. Miller-Rabin exact primality, BigInt values, progress display, copy or download. Runs in your browser. Free.

Parameters
4 - 2000
Filters skip every index 2 mod 4 (divisible by 3) and every multiple of 3 (even). Surviving candidates get a twelve-base Miller-Rabin test.
Lucas primes

          

About Lucas Primes Generator

The Lucas sequence 2, 1, 3, 4, 7, 11, 18, 29, 47, 76, 123, 199, 322... has a secret: sprinkled among those values are primes. L(4) = 7, L(5) = 11, L(7) = 29, L(8) = 47, then a long dry stretch until L(11) = 199 and L(13) = 521. The pattern is elusive — most Lucas numbers are composite, some are even, some are trapped divisible by 3 — and only a scanning test with exact arithmetic can separate the gold from the gravel.

Lucas Primes Generator scans the sequence from index 0 up to any bound you set, skips whole composite families with algebraic filters, and verifies every surviving candidate with a twelve-base Miller-Rabin test on BigInt values. The result is a clean list: index, full decimal value, verification note. Progress phases keep large scans responsive, and one click copies or downloads everything.

Features

  • Complete scan: Every prime in the Lucas sequence up to your chosen maximum index.
  • Algebraic filters: Index families 2 mod 4 (divisible by 3) and multiples of 3 (even) skipped before any test.
  • Exact primality: Miller-Rabin with twelve prime bases — deterministic for every size this tool produces in practice.
  • BigInt values: Full decimal expansion of each prime, no rounding, no exponents.
  • Phased progress: Large scans run in visible phases with live counters and a Stop button.
  • Copy or download: Clean L(n) = value (prime) lines for reports, tests or datasets.
  • Reference tab: The first Lucas primes, the divisibility shortcuts, and the open infinity question.
  • Free and private: Everything runs in the browser — nothing is uploaded, stored or logged.

How to Use

  1. Set the maximum index — where to stop the scan (4 to 2000).
  2. Run the scan — phases tick by with live progress; values get tested the moment their turn arrives.
  3. Read the primes — each row shows the index, the full value and its verification note.
  4. Compare with the reference — L(4) = 7, L(5) = 11, L(7) = 29 should match the first rows exactly.
  5. Copy or download — the complete verified list for further work.

Examples

Example 1 — The seed scan. Max index 20. Expect exactly these six primes: L(4) = 7, L(5) = 11, L(7) = 29, L(8) = 47, L(11) = 199, L(13) = 521, L(16) = 2207, L(17) = 3571, L(19) = 9349 — nine primes, each verified by Miller-Rabin.

Example 2 — The long dry stretch. Scan to 30 and watch the gap: after L(19) = 9349 the next prime appears only at L(31) = 3010349, a 7-digit value separated from its predecessor by twelve composite indexes.

Example 3 — The filters at work. Max index 24. The scan skips L(6), L(10), L(14), L(18), L(22) as multiples of 3 and L(3), L(9), L(15), L(21), L(24) as even — proving most of the sequence dies without a single primality test.

Example 4 — A deep sweep. Max index 200 finds the primes at indexes 31, 37, 41, 53, 61, 71, 79, 113, 131, 151, 173... with values growing to 35 digits — all exact.

Example 5 — Double-check with the checker. Feed L(16) = 2207 into the Fibonacci-prime companion or the Lucas-number checker on this site: the verdict agrees, independent verification in one tab switch.

Benefits

  • Verified list: Every row is a provable prime — the filters and Miller-Rabin run exact checks, not guesses.
  • Speed by algebra: Whole composite families are dismissed before testing, not one by one.
  • Honest spans: The famous gaps between Lucas primes show up exactly as they are — no artificial padding.
  • Workable output: Formatted rows and copy-ready lines serve papers, tests and datasets alike.
  • Responsive scans: Phased execution keeps even 2000-index sweeps interactive.
  • Private by design: Computation stays in the browser; nothing is uploaded or logged.

Frequently Asked Questions

What is a Lucas prime?
A Lucas number that is also prime. The first examples are L(0) = 2, L(2) = 3, L(4) = 7, L(5) = 11, L(7) = 29, L(8) = 47, L(11) = 199, L(13) = 521, L(16) = 2207, L(17) = 3571, L(19) = 9349 and L(31) = 3010349. Most Lucas numbers are composite, so the primes are sparse and famous.
How are the scans made fast?
Two algebraic filters reject most candidates before any primality test: Lucas numbers with index 2 mod 4 (above 2) are always divisible by 3, and indexes divisible by 3 produce even Lucas numbers. Only surviving indexes run the Miller-Rabin test — deterministically exact below 3.3 x 10^24 with the first twelve prime bases.
Is the primality test exact?
For every value this tool emits, yes. Miller-Rabin with bases 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37 is a deterministic proof of primality below about 3.3 x 10^24 and probabilistically certain above it. BigInt arithmetic removes all rounding.
Why are even-indexed Lucas numbers usually composite?
L(2m) relates to L(m) via Fibonacci identities, and the algebraic filters catch most of them outright: L(6) = 18 is even, L(10) = 123 is divisible by 3, L(14) = 843 has both flaws. The surviving even indexes — 4, 8, 16, 40... — are exactly where the rare primes appear.
What ranges can I scan?
Set the maximum index from 4 to 2000. The scan lists every index where the Lucas number is prime, and skips provably composite families. Large ranges run in phases with a live progress readout and a Stop button.
What is the state of the art?
Whether infinitely many Lucas primes exist is an open question. Verified Lucas primes reach far past index 16,000, with each new record needing a serious primality computation — of the same kind this page runs instantly in your browser.
What is in the output?
One row per prime: the index L(n), the full decimal value (formatted for the list), and a verification note. Copy and Download export clean "L(n) = value (prime)" lines for reuse.
Is anything stored or uploaded?
No. Values and primality results are computed in your browser with BigInt. Nothing is sent to a server, saved or logged. Copy or download before closing the tab.