Ulam Spiral — diagonal alignments reveal hidden structure in primes
Ulam spiral: arrange integers in a square spiral, highlight primes. Diagonals align — many polynomials 4n²+bn+c generate dense primes (e.g. 4n²+2n-1). Sacks spiral: n on radius √n, angle proportional to n — primes cluster on arcs corresponding to prime-rich polynomials.