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A graphical representation of the natural numbers in a spiral formation, showing that the prime numbers, when highlighted, tend to fall in clusters and diagonal lines. Also called prime spiral.
[After Stanislaw Marcin Ulam (1909-1984), Polish-born American mathematician who discovered it.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.