What is Conway's Constant?

Look-and-say string lengths: converging to λ ≈ 1.304 per step
23461224668101420263446111211211111221312211n=7n=8n=9n=10n=11n=12n=13

Each sequence is read aloud to produce the next: "1" → "one 1" → "11". Lengths grow irregularly at first but the ratio stabilises at λ ≈ 1.304 (Conway's constant).

Length ratios converge to λ ≈ 1.304
11.331.672λ ≈ 1.304L(n+1) / L(n)nratio

The ratio of consecutive string lengths oscillates but converges to Conway's constant λ ≈ 1.30358.

Conway's cosmological theorem: 92 atomic subsequences
Every look-and-say sequence → 92 atoms in ≤ 24 steps
H (22), He (13112), Li (312), … — named after chemical elements
Each atom grows independently at rate λ ≈ 1.304. Total length grows as λⁿ regardless of start.
What is lambda mathematically?

Lambda is the largest real root of a specific degree-71 polynomial with integer coefficients, derived from the recurrence relations between Conway's 92 atomic subsequences. It is therefore algebraic, not transcendental. This polynomial was computed by Conway and is one of the largest minimal polynomials for any naturally arising constant.

Related topics
Tribonacci Plastic Number Champernowne
Key facts about the Conway Constant

The Conway constant lambda ≈ 1.30357 is the growth rate of the look-and-say sequence 1, 11, 21, 1211, 111221, 312211... John Conway proved in 1986 that after at most 24 steps, any look-and-say sequence breaks into 92 fixed atomic subsequences. Every such sequence grows at exactly rate lambda. Uniquely among naturally arising constants, lambda is algebraic: the largest real root of a specific degree-71 polynomial.

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Who discovered this constant and when?
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