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D-Number


A natural number n>3 such that

 n|(a^(n-2)-a)

whenever (a,n)=1 (a and n are relatively prime) and a<=n. (Here, n|m means that n divides m.) There are an infinite number of such numbers, the first few being 9, 15, 21, 33, 39, 51, ... (OEIS A033553).

The D-numbers are the same as the 3-Knödel numbers.


See also

Divide, Knödel Numbers

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References

Makowski, A. "Generalization of Morrow's D-Numbers." Simon Stevin 36, 71, 1962/1963.Sloane, N. J. A. Sequence A033553 in "The On-Line Encyclopedia of Integer Sequences."

Referenced on Wolfram|Alpha

D-Number

Cite this as:

Weisstein, Eric W. "D-Number." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/D-Number.html

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