Journal of Integer Sequences, Vol. 5 (2002), Article 02.2.1

Carmichael Numbers of the Form (6m+1)(12m+1)(18m+1)

Harvey Dubner

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Ridgewood, NJ 07450


Numbers of the form (6m+1)(12m+1)(18m+1) where all three factors are simultaneously prime are the best known examples of Carmichael numbers. In this paper we tabulate the counts of such numbers up to 10^n for each n <= 42. We also derive a function for estimating these counts that is remarkably accurate.

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(Concerned with sequence A002997 .)

Received August 12, 2002; revised version received September 16, 2002. Published in Journal of Integer Sequences September 23, 2002. Revised version, November 25, 2002.

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