# Definition:Ulam Number

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## Definition

The sequence of **Ulam numbers** is defined as:

- It begins $1, 2, 3$
- Each new term is the next to be uniquely the sum of $2$ previous terms in the sequence.

## Sequence of Ulam Numbers

The sequence of **Ulam numbers** begins as follows:

- $1, 2, 3, 4, 6, 8, 11, 13, 16, 18, 26, 28, 36, 38, 47, 48, 53, 57, 62, 69, \ldots{}$

## Also see

- Results about
**Ulam numbers**can be found here.

## Source of Name

This entry was named for Stanisław Marcin Ulam.

## Sources

- 1997: David Wells:
*Curious and Interesting Numbers*(2nd ed.) ... (previous) ... (next): $11$