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    Keith Number

    Definition

    A Keith number is an n-digit integer N>9 such that 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 taken as 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, 1 + 9 + 7 = 17, 9 + 7 + 17 = 33, 7 + 17 + 33 = 57, 17 + 33 + 57 = 107, 33 + 57 + 107 = 197, ... (Keith). Keith numbers are also called repfigit (repetitive fibonacci-like digit) numbers.

    Related term

    reversal

    Associated person

    Mike Keith

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