# Ulam's game

**Ulam's game**, or the **Rényi–Ulam game**, is a mathematical game similar to the popular game of twenty questions. In Ulam's game, a player attempts to guess an unnamed object or number by asking yes–no questions of another, but *one* of the answers given may be a lie.[1]

Alfréd Rényi (1961) introduced the game in a 1961 paper, based on Hungary's Bar Kokhba game, but the paper was overlooked for many years.

Stanislaw Ulam (1976, p. 281) rediscovered the game, presenting the idea that there are a million objects and the answer to one question can be wrong, and considered the minimum number of questions required, and the strategy that should be adopted.[2] Pelc (2002) gave a survey of similar games and their relation to information theory.

## See also

## References

- "How to Play Ulam's Game" (PDF). Retrieved 13 June 2013.
- Beluhov, Nikolai (2016). "Renyi-Ulam Games and Forbidden Substrings". arXiv:1609.07367 [math.CO].

- Pelc, Andrzej (2002), "Searching games with errors---fifty years of coping with liars",
*Theoretical Computer Science*,**270**(1): 71–109, doi:10.1016/S0304-3975(01)00303-6, ISSN 0304-3975, MR 1871067 - Rényi, Alfréd (1961), "On a problem in information theory",
*Magyar Tud. Akad. Mat. Kutató Int. Közl.*(in Hungarian),**6**: 505–516, MR 0143666 - Ulam, S. M. (1976),
*Adventures of a mathematician*, Charles Scribner's sons, ISBN 978-0-520-07154-4, MR 0485098