Math Goodies Glossary

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Keith Number

A Keith Number is an n-digit integer N with the following property: If a Fibonacci-like sequence (in which each term in the sequence is the sum of the n previous terms) is formed, with the first n terms being the decimal digits of the number N, then N itself occurs as a term in the sequence. For example, 197 is a Keith number since it generates the sequence:

1, 9, 7, 17, 33, 57, 107, 197, ...