Block #305,715

This is the prime chain origin stored in the block header. It is a composite number (not prime itself) — it equals the first prime in the chain multiplied by a primorial. The origin anchors the entire chain to this specific block.

3.166 × 10⁹⁰(91-digit number)

31661701913119747218…20116754701688247999

Discovered Prime Numbers

Lower: 2^k × origin − 1 | Upper: 2^k × origin + 1

These are the actual prime numbers discovered by this block, computed using the verified Primecoin formula. Each number has been independently confirmed to pass the Fermat primality test. Use the FactorDB links to verify any number independently.

Level 0 — Twin Prime Pair (origin ± 1)

origin − 1

3.166 × 10⁹⁰(91-digit number)

31661701913119747218…20116754701688247999

Verify on FactorDB ↗Wolfram Alpha ↗

origin + 1

3.166 × 10⁹⁰(91-digit number)

31661701913119747218…20116754701688248001

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: origin + 1 − origin − 1 = 2 (twin primes ✓)

Level 1 — Twin Prime Pair (2^1 × origin ± 1)

2^1 × origin − 1

6.332 × 10⁹⁰(91-digit number)

63323403826239494437…40233509403376495999

Verify on FactorDB ↗Wolfram Alpha ↗

2^1 × origin + 1

6.332 × 10⁹⁰(91-digit number)

63323403826239494437…40233509403376496001

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: 2^1 × origin + 1 − 2^1 × origin − 1 = 2 (twin primes ✓)

Level 2 — Twin Prime Pair (2^2 × origin ± 1)

2^2 × origin − 1

1.266 × 10⁹¹(92-digit number)

12664680765247898887…80467018806752991999

Verify on FactorDB ↗Wolfram Alpha ↗

2^2 × origin + 1

1.266 × 10⁹¹(92-digit number)

12664680765247898887…80467018806752992001

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: 2^2 × origin + 1 − 2^2 × origin − 1 = 2 (twin primes ✓)

Level 3 — Twin Prime Pair (2^3 × origin ± 1)

2^3 × origin − 1

2.532 × 10⁹¹(92-digit number)

25329361530495797774…60934037613505983999

Verify on FactorDB ↗Wolfram Alpha ↗

2^3 × origin + 1

2.532 × 10⁹¹(92-digit number)

25329361530495797774…60934037613505984001

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: 2^3 × origin + 1 − 2^3 × origin − 1 = 2 (twin primes ✓)

Level 4 — Twin Prime Pair (2^4 × origin ± 1)

2^4 × origin − 1

5.065 × 10⁹¹(92-digit number)

50658723060991595549…21868075227011967999

Verify on FactorDB ↗Wolfram Alpha ↗

What this block proved

The miner who found this block proved the existence of 9 consecutive prime numbers forming a Bi-Twin Chain. The prime chain origin — the large number shown above — anchors the chain and is divisible by a primorial (the product of small primes), cryptographically tying these prime numbers to this specific block.

★☆☆☆☆

Rarity

CommonChain length 9

Found in most blocks. The baseline for Primecoin's proof-of-work.

How Primecoin's Proof-of-Work Constructs These Primes

Primecoin stores a value called the prime chain origin in each block. The miner found a large integer such that when divided by a primorial (the product of small primes: 2 × 3 × 5 × 7 × …), the result is the first prime in the chain. The origin is deliberately divisible by this primorial — that divisibility is part of the proof.

Prime Chain Origin = First Prime × Primorial (2·3·5·7·11·…)

Source: Primecoin prime.cpp — CheckPrimeProofOfWork()

This is why the origin has many small prime factors — those factors are the primorial divisor. The chain then extends from the first prime using the TWN formula:

TWN: twin pairs (p, p+2) where p = origin/primorial − 1 and p+2 = origin/primorial + 1

Cross-reference on Chainz Explorer

Block #305,715

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