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Max N: 10000 Dot size / zoom: 1.0× Spiral starts at: 1 Spiral type Colour mode Highlight polynomial

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Statistics

N—

Primes counted—

Prime density—

Largest prime—

On polynomial—

Hover a cell to inspect the number, primality and factorization.

The Ulam spiral writes 1, 2, 3, … in a square spiral and marks the primes. Surprising diagonal lines appear — many correspond to prime-rich quadratics such as Euler's n²+n+41.