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Dihedral Prime


A number n such that the "LED representation" of n (i.e., the arrangement of horizonal and vertical lines seen on a digital clock or pocket calculator), n upside down, n in a mirror, and n upside-down-and-in-a-mirror are all primes. The digits of n are therefore restricted to 0, 1, 2, 5, and 8. The first few dihedral primes are 2, 5, 11, 101, 181, 1181, 1811, 18181, 108881, 110881, 118081, 120121, ... (OEIS A134996).


See also

Tetradic Number

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References

Rivera, C. "Problems & Puzzles: Puzzle 039-The Mirrorable Numbers (by Mike Keith)." http://www.primepuzzles.net/puzzles/puzz_039.htm.Sloane, N. J. A. Sequence A134996 in "The On-Line Encyclopedia of Integer Sequences."

Referenced on Wolfram|Alpha

Dihedral Prime

Cite this as:

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

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