Ulam Numbers

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The Ulam numbers (or u-numbers) are the sequence defined by , . For , is the least integer uniquely expressible as the sum of two distinct earlier terms. For example, if and , , , and ; because .


This Demonstration shows the Ulam sequence for , , and , highlighting the unique pair of terms that sum to .


Contributed by: Emmanuel Garces Medina (December 2011)
Open content licensed under CC BY-NC-SA



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