The tribonacci sequence generalizes Fibonacci by summing the previous three terms: from seeds 0, 1, 1 it continues 2, 4, 7, 13, 24, 44, 81, 149, 274, 504, 927.
The ratio of consecutive terms converges to the tribonacci constant ≈ 1.839, the real root of \(x^3 = x^2 + x + 1\) — the three-term analogue of the golden ratio. It appears in the geometry of the snub cube, one of the Archimedean solids. Tribonacci numbers count, among other things, binary strings of length \(n\) with no three consecutive zeros.