Ulam Prime SpiralWrite the whole numbers in a square spiral — 1 in the middle, then 2, 3, 4 winding outward — and put a dot on every prime. The dots refuse to scatter randomly: they line up along diagonal streaks, faint but unmistakable.Stanislaw Ulam doodled this in a boring 1963 lecture. Each diagonal is a run of a quadratic like n² + n + 41 (Euler, 1772), which stays prime unusually often — a visible hint of deep, still-unsolved structure in the primes.